cinepakenc: fixes and improvements

version 2013-02-08 Rl
- fixes/optimization in multistrip encoding and codebook size choice,
  quality/bitrate is now better than that of the binary proprietary encoder

version 2013-02-12 Rl
- separated codebook training sets, avoided the transfer of wasted bytes,
  which yields both better quality and smaller files
- now using the correct colorspace (TODO: move conversion to libswscale)

version 2013-02-14 Rl "Valentine's Day" version:
- made strip division more robust
- minimized bruteforcing the number of strips,
  (costs some R/D but speeds up compession a lot), the heuristic
  assumption is that score as a function of the number of strips has
  one wide minimum which moves slowly, of course not fully true
- simplified codebook generation,
  the old code was meant for other optimizations than we actually do
- optimized the codebook generation / error estimation for MODE_MC

version 2013-04-28 Rl
- bugfixed codebook optimization logic

version 2014-01-20 Rl
- made the encoder compatible with vintage decoders
  and added some yet unused code for possible future
  incremental codebook updates
- fixed a small memory leak

version 2014-01-21 Rl
- believe it or not, now we get even smaller files, with better quality
  (which means I missed an optimization earlier :)

Signed-off-by: Diego Biurrun <diego@biurrun.de>

1 files changed, 640 insertions, 194 deletions

diff --git a/libavcodec/cinepakenc.c b/libavcodec/cinepakenc.c
index 2809295d46..1b63260e4d 100644
--- a/libavcodec/cinepakenc.c
+++ b/libavcodec/cinepakenc.c
@@ -1,6 +1,9 @@
 /*
  * Cinepak encoder (c) 2011 Tomas Härdin
  * http://titan.codemill.se/~tomhar/cinepakenc.patch
+ *
+ * Fixes and improvements, vintage decoders compatibility
+ *  (c) 2013, 2014 Rl, Aetey Global Technologies AB
 
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),
@@ -20,13 +23,27 @@ OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 OTHER DEALINGS IN THE SOFTWARE.
 
+ * TODO:
+ * - optimize: color space conversion (move conversion to libswscale), ...
+ * - implement options to set the min/max number of strips?
+ * MAYBE:
+ * - "optimally" split the frame into several non-regular areas
+ *   using a separate codebook pair for each area and approximating
+ *   the area by several rectangular strips (generally not full width ones)
+ *   (use quadtree splitting? a simple fixed-granularity grid?)
  */
 
+#include <string.h>
+
 #include "libavutil/common.h"
+#include "libavutil/internal.h"
 #include "libavutil/intreadwrite.h"
 #include "avcodec.h"
 #include "libavutil/lfg.h"
 #include "elbg.h"
+#include "internal.h"
+
+#include "libavutil/avassert.h"
 
 #define CVID_HEADER_SIZE 10
 #define STRIP_HEADER_SIZE 12
@@ -36,11 +53,20 @@ OTHER DEALINGS IN THE SOFTWARE.
 #define MB_AREA (MB_SIZE*MB_SIZE)
 
 #define VECTOR_MAX 6        //six or four entries per vector depending on format
-#define CODEBOOK_MAX 256
-#define CODEBOOK_NUM 5      //five potential codebooks (1, 4, 16, 64, 256) for V1 and V4
+#define CODEBOOK_MAX 256    //size of a codebook
 
-#define MAX_STRIPS  1       //Note: having fewer choices regarding the number of strip speeds up encoding (obviously)
+//#define MAX_STRIPS  32      //Note: having fewer choices regarding the number of strips speeds up encoding (obviously)
+#define MAX_STRIPS  3       // This seems to be max for vintage players! -- rl
+// TODO: we might want to have a "vintage compatibilty" switch
 #define MIN_STRIPS  1       //Note: having more strips speeds up encoding the frame (this is less obvious)
+// MAX_STRIPS limits the maximum quality you can reach
+//            when you want high quality on high resolutions,
+// MIN_STRIPS limits the minimum efficiently encodable bit rate
+//            on low resolutions
+// the numbers are only used for brute force optimization for the first frame,
+// for the following frames they are adaptively readjusted
+// NOTE the decoder in ffmpeg has its own arbitrary limitation on the number
+// of strips, currently 32
 
 typedef enum {
     MODE_V1_ONLY = 0,
@@ -53,42 +79,51 @@ typedef enum {
 typedef enum {
     ENC_V1,
     ENC_V4,
-    ENC_SKIP
+    ENC_SKIP,
+
+    ENC_UNCERTAIN
 } mb_encoding;
 
 typedef struct {
     int v1_vector;                  //index into v1 codebook
     int v1_error;                   //error when using V1 encoding
-    int v4_vector[CODEBOOK_NUM][4]; //indices into v4 codebooks
-    int v4_error[CODEBOOK_NUM];     //error when using V4 encodings
+    int v4_vector[4];               //indices into v4 codebook
+    int v4_error;                   //error when using V4 encoding
     int skip_error;                 //error when block is skipped (aka copied from last frame)
     mb_encoding best_encoding;      //last result from calculate_mode_score()
 } mb_info;
 
 typedef struct {
     int v1_codebook[CODEBOOK_MAX*VECTOR_MAX];
-    int *v4_codebook;
+    int v4_codebook[CODEBOOK_MAX*VECTOR_MAX];
+    int v1_size;
+    int v4_size;
+    CinepakMode mode;
 } strip_info;
 
 typedef struct {
     AVCodecContext *avctx;
-    unsigned char *pict_bufs[3], *strip_buf, *frame_buf;
-    AVFrame last_frame;
-    AVFrame best_frame;
-    AVFrame scratch_frame;
+    unsigned char *pict_bufs[4], *strip_buf, *frame_buf;
+    AVFrame *last_frame;
+    AVFrame *best_frame;
+    AVFrame *scratch_frame;
+    AVFrame *input_frame;
     enum AVPixelFormat pix_fmt;
     int w, h;
+    int frame_buf_size;
     int curframe, keyint;
     AVLFG randctx;
     uint64_t lambda;
     int *codebook_input;
     int *codebook_closest;
     mb_info *mb;                                //MB RD state
+    int min_strips;          //the current limit
+    int max_strips;          //the current limit
 #ifdef CINEPAKENC_DEBUG
     mb_info *best_mb;                           //TODO: remove. only used for printing stats
-#endif
     int num_v1_mode, num_v4_mode, num_mc_mode;
     int num_v1_encs, num_v4_encs, num_skips;
+#endif
 } CinepakEncContext;
 
 static av_cold int cinepak_encode_init(AVCodecContext *avctx)
@@ -102,20 +137,33 @@ static av_cold int cinepak_encode_init(AVCodecContext *avctx)
         return AVERROR(EINVAL);
     }
 
-    if (!(s->codebook_input = av_malloc(sizeof(int) * (avctx->pix_fmt == AV_PIX_FMT_YUV420P ? 6 : 4) * (avctx->width * avctx->height) >> 2)))
+    if (!(s->last_frame = av_frame_alloc()))
         return AVERROR(ENOMEM);
+    if (!(s->best_frame = av_frame_alloc()))
+        goto enomem;
+    if (!(s->scratch_frame = av_frame_alloc()))
+        goto enomem;
+    if (avctx->pix_fmt == AV_PIX_FMT_RGB24)
+        if (!(s->input_frame = av_frame_alloc()))
+            goto enomem;
+
+    if (!(s->codebook_input = av_malloc(sizeof(int) * (avctx->pix_fmt == AV_PIX_FMT_RGB24 ? 6 : 4) * (avctx->width * avctx->height) >> 2)))
+        goto enomem;
 
     if (!(s->codebook_closest = av_malloc(sizeof(int) * (avctx->width * avctx->height) >> 2)))
         goto enomem;
 
-    for(x = 0; x < 3; x++)
-        if(!(s->pict_bufs[x] = av_malloc((avctx->pix_fmt == AV_PIX_FMT_YUV420P ? 6 : 4) * (avctx->width * avctx->height) >> 2)))
+    for(x = 0; x < (avctx->pix_fmt == AV_PIX_FMT_RGB24 ? 4 : 3); x++)
+        if(!(s->pict_bufs[x] = av_malloc((avctx->pix_fmt == AV_PIX_FMT_RGB24 ? 6 : 4) * (avctx->width * avctx->height) >> 2)))
             goto enomem;
 
     mb_count = avctx->width * avctx->height / MB_AREA;
 
-    //the largest possible chunk is 0x31 with all MBs encoded in V4 mode, which is 34 bits per MB
-    strip_buf_size = STRIP_HEADER_SIZE + 3 * CHUNK_HEADER_SIZE + 2 * VECTOR_MAX * CODEBOOK_MAX + 4 * (mb_count + (mb_count + 15) / 16);
+    //the largest possible chunk is 0x31 with all MBs encoded in V4 mode
+    //and full codebooks being replaced in INTER mode,
+    // which is 34 bits per MB
+    //and 2*256 extra flag bits per strip
+    strip_buf_size = STRIP_HEADER_SIZE + 3 * CHUNK_HEADER_SIZE + 2 * VECTOR_MAX * CODEBOOK_MAX + 4 * (mb_count + (mb_count + 15) / 16) + (2 * CODEBOOK_MAX)/8;
 
     frame_buf_size = CVID_HEADER_SIZE + MAX_STRIPS * strip_buf_size;
 
@@ -137,113 +185,221 @@ static av_cold int cinepak_encode_init(AVCodecContext *avctx)
     s->avctx = avctx;
     s->w = avctx->width;
     s->h = avctx->height;
+    s->frame_buf_size = frame_buf_size;
     s->curframe = 0;
     s->keyint = avctx->keyint_min;
     s->pix_fmt = avctx->pix_fmt;
 
     //set up AVFrames
-    s->last_frame.data[0]        = s->pict_bufs[0];
-    s->last_frame.linesize[0]    = s->w;
-    s->best_frame.data[0]        = s->pict_bufs[1];
-    s->best_frame.linesize[0]    = s->w;
-    s->scratch_frame.data[0]     = s->pict_bufs[2];
-    s->scratch_frame.linesize[0] = s->w;
-
-    if(s->pix_fmt == AV_PIX_FMT_YUV420P) {
-        s->last_frame.data[1]        = s->last_frame.data[0] + s->w * s->h;
-        s->last_frame.data[2]        = s->last_frame.data[1] + ((s->w * s->h) >> 2);
-        s->last_frame.linesize[1]    = s->last_frame.linesize[2] = s->w >> 1;
-
-        s->best_frame.data[1]        = s->best_frame.data[0] + s->w * s->h;
-        s->best_frame.data[2]        = s->best_frame.data[1] + ((s->w * s->h) >> 2);
-        s->best_frame.linesize[1]    = s->best_frame.linesize[2] = s->w >> 1;
-
-        s->scratch_frame.data[1]     = s->scratch_frame.data[0] + s->w * s->h;
-        s->scratch_frame.data[2]     = s->scratch_frame.data[1] + ((s->w * s->h) >> 2);
-        s->scratch_frame.linesize[1] = s->scratch_frame.linesize[2] = s->w >> 1;
+    s->last_frame->data[0]        = s->pict_bufs[0];
+    s->last_frame->linesize[0]    = s->w;
+    s->best_frame->data[0]        = s->pict_bufs[1];
+    s->best_frame->linesize[0]    = s->w;
+    s->scratch_frame->data[0]     = s->pict_bufs[2];
+    s->scratch_frame->linesize[0] = s->w;
+
+    if (s->pix_fmt == AV_PIX_FMT_RGB24) {
+        s->last_frame->data[1]        = s->last_frame->data[0] + s->w * s->h;
+        s->last_frame->data[2]        = s->last_frame->data[1] + ((s->w * s->h) >> 2);
+        s->last_frame->linesize[1]    = s->last_frame->linesize[2] = s->w >> 1;
+
+        s->best_frame->data[1]        = s->best_frame->data[0] + s->w * s->h;
+        s->best_frame->data[2]        = s->best_frame->data[1] + ((s->w * s->h) >> 2);
+        s->best_frame->linesize[1]    = s->best_frame->linesize[2] = s->w >> 1;
+
+        s->scratch_frame->data[1]     = s->scratch_frame->data[0] + s->w * s->h;
+        s->scratch_frame->data[2]     = s->scratch_frame->data[1] + ((s->w * s->h) >> 2);
+        s->scratch_frame->linesize[1] = s->scratch_frame->linesize[2] = s->w >> 1;
+
+        s->input_frame->data[0]       = s->pict_bufs[3];
+        s->input_frame->linesize[0]   = s->w;
+        s->input_frame->data[1]       = s->input_frame->data[0] + s->w * s->h;
+        s->input_frame->data[2]       = s->input_frame->data[1] + ((s->w * s->h) >> 2);
+        s->input_frame->linesize[1]   = s->input_frame->linesize[2] = s->w >> 1;
     }
 
+    s->min_strips = MIN_STRIPS;
+    s->max_strips = MAX_STRIPS;
+
+#ifdef CINEPAKENC_DEBUG
     s->num_v1_mode = s->num_v4_mode = s->num_mc_mode = s->num_v1_encs = s->num_v4_encs = s->num_skips = 0;
+#endif
 
     return 0;
 
 enomem:
-    av_free(s->codebook_input);
-    av_free(s->codebook_closest);
-    av_free(s->strip_buf);
-    av_free(s->frame_buf);
-    av_free(s->mb);
+    av_frame_free(&s->last_frame);
+    av_frame_free(&s->best_frame);
+    av_frame_free(&s->scratch_frame);
+    if (avctx->pix_fmt == AV_PIX_FMT_RGB24)
+        av_frame_free(&s->input_frame);
+    av_freep(&s->codebook_input);
+    av_freep(&s->codebook_closest);
+    av_freep(&s->strip_buf);
+    av_freep(&s->frame_buf);
+    av_freep(&s->mb);
 #ifdef CINEPAKENC_DEBUG
-    av_free(s->best_mb);
+    av_freep(&s->best_mb);
 #endif
 
-    for(x = 0; x < 3; x++)
-        av_free(s->pict_bufs[x]);
+    for(x = 0; x < (avctx->pix_fmt == AV_PIX_FMT_RGB24 ? 4 : 3); x++)
+        av_freep(&s->pict_bufs[x]);
 
     return AVERROR(ENOMEM);
 }
 
-static int64_t calculate_mode_score(CinepakEncContext *s, CinepakMode mode, int h, int v1_size, int v4_size, int v4, strip_info *info)
+static int64_t calculate_mode_score(CinepakEncContext *s, int h, strip_info *info, int report, int *training_set_v1_shrunk, int *training_set_v4_shrunk
+#ifdef CINEPAK_REPORT_SERR
+, int64_t *serr
+#endif
+)
 {
     //score = FF_LAMBDA_SCALE * error + lambda * bits
     int x;
-    int entry_size = s->pix_fmt == AV_PIX_FMT_YUV420P ? 6 : 4;
+    int entry_size = s->pix_fmt == AV_PIX_FMT_RGB24 ? 6 : 4;
     int mb_count = s->w * h / MB_AREA;
     mb_info *mb;
     int64_t score1, score2, score3;
-    int64_t ret = s->lambda * ((v1_size ? CHUNK_HEADER_SIZE + v1_size * entry_size : 0) +
-                   (v4_size ? CHUNK_HEADER_SIZE + v4_size * entry_size : 0) +
+    int64_t ret = s->lambda * ((info->v1_size ? CHUNK_HEADER_SIZE + info->v1_size * entry_size : 0) +
+                   (info->v4_size ? CHUNK_HEADER_SIZE + info->v4_size * entry_size : 0) +
                    CHUNK_HEADER_SIZE) << 3;
 
-    //av_log(s->avctx, AV_LOG_INFO, "sizes %3i %3i -> %9li score mb_count %i", v1_size, v4_size, ret, mb_count);
+    //av_log(s->avctx, AV_LOG_INFO, "sizes %3i %3i -> %9lli score mb_count %i", info->v1_size, info->v4_size, (long long int)ret, mb_count);
+
+#ifdef CINEPAK_REPORT_SERR
+    *serr = 0;
+#endif
 
-    switch(mode) {
+    switch(info->mode) {
     case MODE_V1_ONLY:
         //one byte per MB
         ret += s->lambda * 8 * mb_count;
 
+// while calculating we assume all blocks are ENC_V1
         for(x = 0; x < mb_count; x++) {
             mb = &s->mb[x];
             ret += FF_LAMBDA_SCALE * mb->v1_error;
+#ifdef CINEPAK_REPORT_SERR
+            *serr += mb->v1_error;
+#endif
+// this function is never called for report in MODE_V1_ONLY
+//            if(!report)
             mb->best_encoding = ENC_V1;
         }
 
         break;
     case MODE_V1_V4:
         //9 or 33 bits per MB
-        for(x = 0; x < mb_count; x++) {
-            mb = &s->mb[x];
-            score1 = s->lambda * 9  + FF_LAMBDA_SCALE * mb->v1_error;
-            score2 = s->lambda * 33 + FF_LAMBDA_SCALE * mb->v4_error[v4];
-
-            if(score1 <= score2) {
+        if(report) {
+// no moves between the corresponding training sets are allowed
+            *training_set_v1_shrunk = *training_set_v4_shrunk = 0;
+            for(x = 0; x < mb_count; x++) {
+                int mberr;
+                mb = &s->mb[x];
+                if(mb->best_encoding == ENC_V1)
+                    score1 = s->lambda * 9  + FF_LAMBDA_SCALE * (mberr=mb->v1_error);
+                else
+                    score1 = s->lambda * 33 + FF_LAMBDA_SCALE * (mberr=mb->v4_error);
                 ret += score1;
-                mb->best_encoding = ENC_V1;
-            } else {
-                ret += score2;
-                mb->best_encoding = ENC_V4;
+#ifdef CINEPAK_REPORT_SERR
+                *serr += mberr;
+#endif
+            }
+        } else { // find best mode per block
+            for(x = 0; x < mb_count; x++) {
+                mb = &s->mb[x];
+                score1 = s->lambda * 9  + FF_LAMBDA_SCALE * mb->v1_error;
+                score2 = s->lambda * 33 + FF_LAMBDA_SCALE * mb->v4_error;
+
+                if(score1 <= score2) {
+                    ret += score1;
+#ifdef CINEPAK_REPORT_SERR
+                    *serr += mb->v1_error;
+#endif
+                    mb->best_encoding = ENC_V1;
+                } else {
+                    ret += score2;
+#ifdef CINEPAK_REPORT_SERR
+                    *serr += mb->v4_error;
+#endif
+                    mb->best_encoding = ENC_V4;
+                }
             }
         }
 
         break;
     case MODE_MC:
         //1, 10 or 34 bits per MB
-        for(x = 0; x < mb_count; x++) {
-            mb = &s->mb[x];
-            score1 = s->lambda * 1  + FF_LAMBDA_SCALE * mb->skip_error;
-            score2 = s->lambda * 10 + FF_LAMBDA_SCALE * mb->v1_error;
-            score3 = s->lambda * 34 + FF_LAMBDA_SCALE * mb->v4_error[v4];
-
-
-            if(score1 <= score2 && score1 <= score3) {
-                ret += score1;
-                mb->best_encoding = ENC_SKIP;
-            } else if(score2 <= score1 && score2 <= score3) {
-                ret += score2;
-                mb->best_encoding = ENC_V1;
-            } else {
-                ret += score3;
-                mb->best_encoding = ENC_V4;
+        if(report) {
+            int v1_shrunk = 0, v4_shrunk = 0;
+            for(x = 0; x < mb_count; x++) {
+                mb = &s->mb[x];
+// it is OK to move blocks to ENC_SKIP here
+// but not to any codebook encoding!
+                score1 = s->lambda * 1  + FF_LAMBDA_SCALE * mb->skip_error;
+                if(mb->best_encoding == ENC_SKIP) {
+                    ret += score1;
+#ifdef CINEPAK_REPORT_SERR
+                    *serr += mb->skip_error;
+#endif
+                } else if(mb->best_encoding == ENC_V1) {
+                    if((score2=s->lambda * 10 + FF_LAMBDA_SCALE * mb->v1_error) >= score1) {
+                        mb->best_encoding = ENC_SKIP;
+                        ++v1_shrunk;
+                        ret += score1;
+#ifdef CINEPAK_REPORT_SERR
+                        *serr += mb->skip_error;
+#endif
+                    } else {
+                        ret += score2;
+#ifdef CINEPAK_REPORT_SERR
+                        *serr += mb->v1_error;
+#endif
+                    }
+                } else {
+                    if((score3=s->lambda * 34 + FF_LAMBDA_SCALE * mb->v4_error) >= score1) {
+                        mb->best_encoding = ENC_SKIP;
+                        ++v4_shrunk;
+                        ret += score1;
+#ifdef CINEPAK_REPORT_SERR
+                        *serr += mb->skip_error;
+#endif
+                    } else {
+                        ret += score3;
+#ifdef CINEPAK_REPORT_SERR
+                        *serr += mb->v4_error;
+#endif
+                    }
+                }
+            }
+            *training_set_v1_shrunk = v1_shrunk;
+            *training_set_v4_shrunk = v4_shrunk;
+        } else { // find best mode per block
+            for(x = 0; x < mb_count; x++) {
+                mb = &s->mb[x];
+                score1 = s->lambda * 1  + FF_LAMBDA_SCALE * mb->skip_error;
+                score2 = s->lambda * 10 + FF_LAMBDA_SCALE * mb->v1_error;
+                score3 = s->lambda * 34 + FF_LAMBDA_SCALE * mb->v4_error;
+
+                if(score1 <= score2 && score1 <= score3) {
+                    ret += score1;
+#ifdef CINEPAK_REPORT_SERR
+                    *serr += mb->skip_error;
+#endif
+                    mb->best_encoding = ENC_SKIP;
+                } else if(score2 <= score3) {
+                    ret += score2;
+#ifdef CINEPAK_REPORT_SERR
+                    *serr += mb->v1_error;
+#endif
+                    mb->best_encoding = ENC_V1;
+                } else {
+                    ret += score3;
+#ifdef CINEPAK_REPORT_SERR
+                    *serr += mb->v4_error;
+#endif
+                    mb->best_encoding = ENC_V4;
+                }
             }
         }
 
@@ -262,13 +418,45 @@ static int write_chunk_header(unsigned char *buf, int chunk_type, int chunk_size
 
 static int encode_codebook(CinepakEncContext *s, int *codebook, int size, int chunk_type_yuv, int chunk_type_gray, unsigned char *buf)
 {
-    int x, y, ret, entry_size = s->pix_fmt == AV_PIX_FMT_YUV420P ? 6 : 4;
-
-    ret = write_chunk_header(buf, s->pix_fmt == AV_PIX_FMT_YUV420P ? chunk_type_yuv : chunk_type_gray, entry_size * size);
-
-    for(x = 0; x < size; x++)
-        for(y = 0; y < entry_size; y++)
-            buf[ret++] = codebook[y + x*entry_size] ^ (y >= 4 ? 0x80 : 0);
+    int x, y, ret, entry_size = s->pix_fmt == AV_PIX_FMT_RGB24 ? 6 : 4;
+    int incremental_codebook_replacement_mode = 0; // hardcoded here,
+                // the compiler should notice that this is a constant -- rl
+
+    ret = write_chunk_header(buf,
+          s->pix_fmt == AV_PIX_FMT_RGB24 ?
+           chunk_type_yuv+(incremental_codebook_replacement_mode?1:0) :
+           chunk_type_gray+(incremental_codebook_replacement_mode?1:0),
+          entry_size * size
+           + (incremental_codebook_replacement_mode?(size+31)/32*4:0) );
+
+// we do codebook encoding according to the "intra" mode
+// but we keep the "dead" code for reference in case we will want
+// to use incremental codebook updates (which actually would give us
+// "kind of" motion compensation, especially in 1 strip/frame case) -- rl
+// (of course, the code will be not useful as-is)
+    if(incremental_codebook_replacement_mode) {
+        int flags = 0;
+        int flagsind;
+        for(x = 0; x < size; x++) {
+            if(flags == 0) {
+                flagsind = ret;
+                ret += 4;
+                flags = 0x80000000;
+            } else
+                flags = ((flags>>1) | 0x80000000);
+            for(y = 0; y < entry_size; y++)
+                buf[ret++] = codebook[y + x*entry_size] ^ (y >= 4 ? 0x80 : 0);
+            if((flags&0xffffffff) == 0xffffffff) {
+                AV_WB32(&buf[flagsind], flags);
+                flags = 0;
+            }
+        }
+        if(flags)
+            AV_WB32(&buf[flagsind], flags);
+    } else
+        for(x = 0; x < size; x++)
+            for(y = 0; y < entry_size; y++)
+                buf[ret++] = codebook[y + x*entry_size] ^ (y >= 4 ? 0x80 : 0);
 
     return ret;
 }
@@ -279,7 +467,7 @@ static void get_sub_picture(CinepakEncContext *s, int x, int y, AVPicture *in, A
     out->data[0] = in->data[0] + x + y * in->linesize[0];
     out->linesize[0] = in->linesize[0];
 
-    if(s->pix_fmt == AV_PIX_FMT_YUV420P) {
+    if(s->pix_fmt == AV_PIX_FMT_RGB24) {
         out->data[1] = in->data[1] + (x >> 1) + (y >> 1) * in->linesize[1];
         out->linesize[1] = in->linesize[1];
 
@@ -289,47 +477,47 @@ static void get_sub_picture(CinepakEncContext *s, int x, int y, AVPicture *in, A
 }
 
 //decodes the V1 vector in mb into the 4x4 MB pointed to by sub_pict
-static void decode_v1_vector(CinepakEncContext *s, AVPicture *sub_pict, mb_info *mb, strip_info *info)
+static void decode_v1_vector(CinepakEncContext *s, AVPicture *sub_pict, int v1_vector, strip_info *info)
 {
-    int entry_size = s->pix_fmt == AV_PIX_FMT_YUV420P ? 6 : 4;
+    int entry_size = s->pix_fmt == AV_PIX_FMT_RGB24 ? 6 : 4;
 
     sub_pict->data[0][0] =
             sub_pict->data[0][1] =
             sub_pict->data[0][    sub_pict->linesize[0]] =
-            sub_pict->data[0][1+  sub_pict->linesize[0]] = info->v1_codebook[mb->v1_vector*entry_size];
+            sub_pict->data[0][1+  sub_pict->linesize[0]] = info->v1_codebook[v1_vector*entry_size];
 
     sub_pict->data[0][2] =
             sub_pict->data[0][3] =
             sub_pict->data[0][2+  sub_pict->linesize[0]] =
-            sub_pict->data[0][3+  sub_pict->linesize[0]] = info->v1_codebook[mb->v1_vector*entry_size+1];
+            sub_pict->data[0][3+  sub_pict->linesize[0]] = info->v1_codebook[v1_vector*entry_size+1];
 
     sub_pict->data[0][2*sub_pict->linesize[0]] =
             sub_pict->data[0][1+2*sub_pict->linesize[0]] =
             sub_pict->data[0][  3*sub_pict->linesize[0]] =
-            sub_pict->data[0][1+3*sub_pict->linesize[0]] = info->v1_codebook[mb->v1_vector*entry_size+2];
+            sub_pict->data[0][1+3*sub_pict->linesize[0]] = info->v1_codebook[v1_vector*entry_size+2];
 
     sub_pict->data[0][2+2*sub_pict->linesize[0]] =
             sub_pict->data[0][3+2*sub_pict->linesize[0]] =
             sub_pict->data[0][2+3*sub_pict->linesize[0]] =
-            sub_pict->data[0][3+3*sub_pict->linesize[0]] = info->v1_codebook[mb->v1_vector*entry_size+3];
+            sub_pict->data[0][3+3*sub_pict->linesize[0]] = info->v1_codebook[v1_vector*entry_size+3];
 
-    if(s->pix_fmt == AV_PIX_FMT_YUV420P) {
+    if(s->pix_fmt == AV_PIX_FMT_RGB24) {
         sub_pict->data[1][0] =
             sub_pict->data[1][1] =
             sub_pict->data[1][    sub_pict->linesize[1]] =
-            sub_pict->data[1][1+  sub_pict->linesize[1]] = info->v1_codebook[mb->v1_vector*entry_size+4];
+            sub_pict->data[1][1+  sub_pict->linesize[1]] = info->v1_codebook[v1_vector*entry_size+4];
 
         sub_pict->data[2][0] =
             sub_pict->data[2][1] =
             sub_pict->data[2][    sub_pict->linesize[2]] =
-            sub_pict->data[2][1+  sub_pict->linesize[2]] = info->v1_codebook[mb->v1_vector*entry_size+5];
+            sub_pict->data[2][1+  sub_pict->linesize[2]] = info->v1_codebook[v1_vector*entry_size+5];
     }
 }
 
 //decodes the V4 vectors in mb into the 4x4 MB pointed to by sub_pict
 static void decode_v4_vector(CinepakEncContext *s, AVPicture *sub_pict, int *v4_vector, strip_info *info)
 {
-    int i, x, y, entry_size = s->pix_fmt == AV_PIX_FMT_YUV420P ? 6 : 4;
+    int i, x, y, entry_size = s->pix_fmt == AV_PIX_FMT_RGB24 ? 6 : 4;
 
     for(i = y = 0; y < 4; y += 2) {
         for(x = 0; x < 4; x += 2, i++) {
@@ -338,7 +526,7 @@ static void decode_v4_vector(CinepakEncContext *s, AVPicture *sub_pict, int *v4_
             sub_pict->data[0][x   + (y+1)*sub_pict->linesize[0]] = info->v4_codebook[v4_vector[i]*entry_size+2];
             sub_pict->data[0][x+1 + (y+1)*sub_pict->linesize[0]] = info->v4_codebook[v4_vector[i]*entry_size+3];
 
-            if(s->pix_fmt == AV_PIX_FMT_YUV420P) {
+            if(s->pix_fmt == AV_PIX_FMT_RGB24) {
                 sub_pict->data[1][(x>>1) + (y>>1)*sub_pict->linesize[1]] = info->v4_codebook[v4_vector[i]*entry_size+4];
                 sub_pict->data[2][(x>>1) + (y>>1)*sub_pict->linesize[2]] = info->v4_codebook[v4_vector[i]*entry_size+5];
             }
@@ -346,39 +534,62 @@ static void decode_v4_vector(CinepakEncContext *s, AVPicture *sub_pict, int *v4_
     }
 }
 
-static int encode_mode(CinepakEncContext *s, CinepakMode mode, int h, int v1_size, int v4_size, int v4, AVPicture *scratch_pict, strip_info *info, unsigned char *buf)
+static void copy_mb(CinepakEncContext *s, AVPicture *a, AVPicture *b)
+{
+    int y, p;
+
+    for(y = 0; y < MB_SIZE; y++) {
+        memcpy(a->data[0]+y*a->linesize[0], b->data[0]+y*b->linesize[0],
+               MB_SIZE);
+    }
+
+    if(s->pix_fmt == AV_PIX_FMT_RGB24) {
+        for(p = 1; p <= 2; p++) {
+            for(y = 0; y < MB_SIZE/2; y++) {
+                memcpy(a->data[p] + y*a->linesize[p],
+                       b->data[p] + y*b->linesize[p],
+                       MB_SIZE/2);
+            }
+        }
+    }
+}
+
+static int encode_mode(CinepakEncContext *s, int h, AVPicture *scratch_pict, AVPicture *last_pict, strip_info *info, unsigned char *buf)
 {
     int x, y, z, flags, bits, temp_size, header_ofs, ret = 0, mb_count = s->w * h / MB_AREA;
     int needs_extra_bit, should_write_temp;
     unsigned char temp[64]; //32/2 = 16 V4 blocks at 4 B each -> 64 B
     mb_info *mb;
-    AVPicture sub_scratch;
+    AVPicture sub_scratch, sub_last;
 
     //encode codebooks
-    if(v1_size)
-        ret += encode_codebook(s, info->v1_codebook, v1_size, 0x22, 0x26, buf + ret);
+////// MacOS vintage decoder compatibility dictates the presence of
+////// the codebook chunk even when the codebook is empty - pretty dumb...
+////// and also the certain order of the codebook chunks -- rl
+//    if(info->v4_size)
+        ret += encode_codebook(s, info->v4_codebook, info->v4_size, 0x20, 0x24, buf + ret);
 
-    if(v4_size)
-        ret += encode_codebook(s, info->v4_codebook, v4_size, 0x20, 0x24, buf + ret);
+//    if(info->v1_size)
+        ret += encode_codebook(s, info->v1_codebook, info->v1_size, 0x22, 0x26, buf + ret);
 
     //update scratch picture
     for(z = y = 0; y < h; y += MB_SIZE) {
         for(x = 0; x < s->w; x += MB_SIZE, z++) {
             mb = &s->mb[z];
 
-            if(mode == MODE_MC && mb->best_encoding == ENC_SKIP)
-                continue;
-
             get_sub_picture(s, x, y, scratch_pict, &sub_scratch);
 
-            if(mode == MODE_V1_ONLY || mb->best_encoding == ENC_V1)
-                decode_v1_vector(s, &sub_scratch, mb, info);
-            else if(mode != MODE_V1_ONLY && mb->best_encoding == ENC_V4)
-                decode_v4_vector(s, &sub_scratch, mb->v4_vector[v4], info);
+            if(info->mode == MODE_MC && mb->best_encoding == ENC_SKIP) {
+                get_sub_picture(s, x, y, last_pict, &sub_last);
+                copy_mb(s, &sub_scratch, &sub_last);
+            } else if(info->mode == MODE_V1_ONLY || mb->best_encoding == ENC_V1)
+                decode_v1_vector(s, &sub_scratch, mb->v1_vector, info);
+            else
+                decode_v4_vector(s, &sub_scratch, mb->v4_vector, info);
         }
     }
 
-    switch(mode) {
+    switch(info->mode) {
     case MODE_V1_ONLY:
         //av_log(s->avctx, AV_LOG_INFO, "mb_count = %i\n", mb_count);
         ret += write_chunk_header(buf + ret, 0x32, mb_count);
@@ -408,7 +619,7 @@ static int encode_mode(CinepakEncContext *s, CinepakMode mode, int h, int v1_siz
                     buf[ret++] = mb->v1_vector;
                 else
                     for(z = 0; z < 4; z++)
-                        buf[ret++] = mb->v4_vector[v4][z];
+                        buf[ret++] = mb->v4_vector[z];
             }
         }
 
@@ -456,7 +667,7 @@ static int encode_mode(CinepakEncContext *s, CinepakMode mode, int h, int v1_siz
                 temp[temp_size++] = mb->v1_vector;
             else if(mb->best_encoding == ENC_V4)
                 for(z = 0; z < 4; z++)
-                    temp[temp_size++] = mb->v4_vector[v4][z];
+                    temp[temp_size++] = mb->v4_vector[z];
 
             if(should_write_temp) {
                 memcpy(&buf[ret], temp, temp_size);
@@ -492,7 +703,7 @@ static int compute_mb_distortion(CinepakEncContext *s, AVPicture *a, AVPicture *
         }
     }
 
-    if(s->pix_fmt == AV_PIX_FMT_YUV420P) {
+    if(s->pix_fmt == AV_PIX_FMT_RGB24) {
         for(p = 1; p <= 2; p++) {
             for(y = 0; y < MB_SIZE/2; y++) {
                 for(x = 0; x < MB_SIZE/2; x++) {
@@ -506,19 +717,30 @@ static int compute_mb_distortion(CinepakEncContext *s, AVPicture *a, AVPicture *
     return ret;
 }
 
-static int quantize(CinepakEncContext *s, int h, AVPicture *pict, int v1mode, int size, int v4, strip_info *info)
+// return the possibly adjusted size of the codebook
+#define CERTAIN(x) ((x)!=ENC_UNCERTAIN)
+static int quantize(CinepakEncContext *s, int h, AVPicture *pict,
+                    int v1mode, strip_info *info,
+                    mb_encoding encoding)
 {
-    int x, y, i, j, k, x2, y2, x3, y3, plane, shift;
-    int entry_size = s->pix_fmt == AV_PIX_FMT_YUV420P ? 6 : 4;
+    int x, y, i, j, k, x2, y2, x3, y3, plane, shift, mbn;
+    int entry_size = s->pix_fmt == AV_PIX_FMT_RGB24 ? 6 : 4;
     int *codebook = v1mode ? info->v1_codebook : info->v4_codebook;
+    int size = v1mode ? info->v1_size : info->v4_size;
     int64_t total_error = 0;
     uint8_t vq_pict_buf[(MB_AREA*3)/2];
     AVPicture sub_pict, vq_pict;
 
-    for(i = y = 0; y < h; y += MB_SIZE) {
-        for(x = 0; x < s->w; x += MB_SIZE, i += v1mode ? 1 : 4) {
-            int *base = s->codebook_input + i*entry_size;
+    for(mbn = i = y = 0; y < h; y += MB_SIZE) {
+        for(x = 0; x < s->w; x += MB_SIZE, ++mbn) {
+            int *base;
 
+            if(CERTAIN(encoding)) {
+// use for the training only the blocks known to be to be encoded [sic:-]
+               if(s->mb[mbn].best_encoding != encoding) continue;
+            }
+
+            base = s->codebook_input + i*entry_size;
             if(v1mode) {
                 //subsample
                 for(j = y2 = 0; y2 < entry_size; y2 += 2) {
@@ -553,8 +775,19 @@ static int quantize(CinepakEncContext *s, int h, AVPicture *pict, int v1mode, in
                     }
                 }
             }
+            i += v1mode ? 1 : 4;
         }
     }
+//    if(i < mbn*(v1mode ? 1 : 4)) {
+//        av_log(s->avctx, AV_LOG_INFO, "reducing training set for %s from %i to %i (encoding %i)\n", v1mode?"v1":"v4", mbn*(v1mode ? 1 : 4), i, encoding);
+//    }
+
+    if(i == 0) // empty training set, nothing to do
+        return 0;
+    if(i < size) {
+        //av_log(s->avctx, (CERTAIN(encoding) ? AV_LOG_ERROR : AV_LOG_INFO), "WOULD WASTE: %s cbsize %i bigger than training set size %i (encoding %i)\n", v1mode?"v1":"v4", size, i, encoding);
+        size = i;
+    }
 
     ff_init_elbg(s->codebook_input, entry_size, i, codebook, size, 1, s->codebook_closest, &s->randctx);
     ff_do_elbg(s->codebook_input, entry_size, i, codebook, size, 1, s->codebook_closest, &s->randctx);
@@ -568,8 +801,11 @@ static int quantize(CinepakEncContext *s, int h, AVPicture *pict, int v1mode, in
 
     //copy indices
     for(i = j = y = 0; y < h; y += MB_SIZE) {
-        for(x = 0; x < s->w; x += MB_SIZE, j++, i += v1mode ? 1 : 4) {
+        for(x = 0; x < s->w; x += MB_SIZE, j++) {
             mb_info *mb = &s->mb[j];
+// skip uninteresting blocks if we know their preferred encoding
+            if(CERTAIN(encoding) && mb->best_encoding != encoding)
+                continue;
 
             //point sub_pict to current MB
             get_sub_picture(s, x, y, pict, &sub_pict);
@@ -578,26 +814,29 @@ static int quantize(CinepakEncContext *s, int h, AVPicture *pict, int v1mode, in
                 mb->v1_vector = s->codebook_closest[i];
 
                 //fill in vq_pict with V1 data
-                decode_v1_vector(s, &vq_pict, mb, info);
+                decode_v1_vector(s, &vq_pict, mb->v1_vector, info);
 
                 mb->v1_error = compute_mb_distortion(s, &sub_pict, &vq_pict);
                 total_error += mb->v1_error;
             } else {
                 for(k = 0; k < 4; k++)
-                    mb->v4_vector[v4][k] = s->codebook_closest[i+k];
+                    mb->v4_vector[k] = s->codebook_closest[i+k];
 
                 //fill in vq_pict with V4 data
-                decode_v4_vector(s, &vq_pict, mb->v4_vector[v4], info);
+                decode_v4_vector(s, &vq_pict, mb->v4_vector, info);
 
-                mb->v4_error[v4] = compute_mb_distortion(s, &sub_pict, &vq_pict);
-                total_error += mb->v4_error[v4];
+                mb->v4_error = compute_mb_distortion(s, &sub_pict, &vq_pict);
+                total_error += mb->v4_error;
             }
+            i += v1mode ? 1 : 4;
         }
     }
+// check that we did it right in the beginning of the function
+    av_assert0(i >= size); // training set is no smaller than the codebook
 
-    //av_log(s->avctx, AV_LOG_INFO, "mode %i size %i i %i error %li\n", v1mode, size, i, total_error);
+    //av_log(s->avctx, AV_LOG_INFO, "isv1 %i size= %i i= %i error %lli\n", v1mode, size, i, (long long int)total_error);
 
-    return 0;
+    return size;
 }
 
 static void calculate_skip_errors(CinepakEncContext *s, int h, AVPicture *last_pict, AVPicture *pict, strip_info *info)
@@ -617,59 +856,151 @@ static void calculate_skip_errors(CinepakEncContext *s, int h, AVPicture *last_p
 
 static void write_strip_header(CinepakEncContext *s, int y, int h, int keyframe, unsigned char *buf, int strip_size)
 {
-    buf[0] = keyframe ? 0x11: 0x10;
+// actually we are exclusively using intra strip coding (how much can we win
+// otherwise? how to choose which part of a codebook to update?),
+// keyframes are different only because we disallow ENC_SKIP on them -- rl
+// (besides, the logic here used to be inverted: )
+//    buf[0] = keyframe ? 0x11: 0x10;
+    buf[0] = keyframe ? 0x10: 0x11;
     AV_WB24(&buf[1], strip_size + STRIP_HEADER_SIZE);
-    AV_WB16(&buf[4], y);
+//    AV_WB16(&buf[4], y); /* using absolute y values works -- rl */
+    AV_WB16(&buf[4], 0); /* using relative values works as well -- rl */
     AV_WB16(&buf[6], 0);
-    AV_WB16(&buf[8], h);
+//    AV_WB16(&buf[8], y+h); /* using absolute y values works -- rl */
+    AV_WB16(&buf[8], h); /* using relative values works as well -- rl */
     AV_WB16(&buf[10], s->w);
+    //av_log(s->avctx, AV_LOG_INFO, "write_strip_header() %x keyframe=%d\n", buf[0], keyframe);
 }
 
-static int rd_strip(CinepakEncContext *s, int y, int h, int keyframe, AVPicture *last_pict, AVPicture *pict, AVPicture *scratch_pict, unsigned char *buf, int64_t *best_score)
+static int rd_strip(CinepakEncContext *s, int y, int h, int keyframe, AVPicture *last_pict, AVPicture *pict, AVPicture *scratch_pict, unsigned char *buf, int64_t *best_score
+#ifdef CINEPAK_REPORT_SERR
+, int64_t *best_serr
+#endif
+)
 {
     int64_t score = 0;
-    int best_size = 0, v1_size, v4_size, v4, mb_count = s->w * h / MB_AREA;
+#ifdef CINEPAK_REPORT_SERR
+    int64_t serr;
+#endif
+    int best_size = 0;
     strip_info info;
-    CinepakMode best_mode;
-    int v4_codebooks[CODEBOOK_NUM][CODEBOOK_MAX*VECTOR_MAX];
+// for codebook optimization:
+    int v1enough, v1_size, v4enough, v4_size;
+    int new_v1_size, new_v4_size;
+    int v1shrunk, v4shrunk;
 
     if(!keyframe)
         calculate_skip_errors(s, h, last_pict, pict, &info);
 
-    //precompute V4 codebooks
-    for(v4_size = 1, v4 = 0; v4_size <= 256; v4_size <<= 2, v4++) {
-        info.v4_codebook = v4_codebooks[v4];
-        quantize(s, h, pict, 0, v4_size, v4, &info);
-    }
-
-    //try all powers of 4 for the size of the codebooks
-    //constraint the v4 codebook to be no bigger than the v1 codebook
-    for(v1_size = 1; v1_size <= 256; v1_size <<= 2) {
-        //compute V1 codebook
-        quantize(s, h, pict, 1, v1_size, -1, &info);
-
-        for(v4_size = 0, v4 = -1; v4_size <= v1_size; v4_size = v4_size ? v4_size << 2 : v1_size >= 4 ? v1_size >> 2 : 1, v4++) {
+    //try some powers of 4 for the size of the codebooks
+    //constraint the v4 codebook to be no bigger than v1 one,
+    //(and no less than v1_size/4)
+    //thus making v1 preferable and possibly losing small details? should be ok
+#define SMALLEST_CODEBOOK 1
+    for(v1enough = 0, v1_size = SMALLEST_CODEBOOK; v1_size <= CODEBOOK_MAX && !v1enough; v1_size <<= 2) {
+        for(v4enough = 0, v4_size = 0; v4_size <= v1_size && !v4enough; v4_size = v4_size ? v4_size << 2 : v1_size >= SMALLEST_CODEBOOK << 2 ? v1_size >> 2 : SMALLEST_CODEBOOK) {
             //try all modes
             for(CinepakMode mode = 0; mode < MODE_COUNT; mode++) {
-                //don't allow MODE_MC in inter frames
+                //don't allow MODE_MC in intra frames
                 if(keyframe && mode == MODE_MC)
                     continue;
 
-                //only allow V1-only mode if v4 codebook is empty
-                if(!v4_size && mode != MODE_V1_ONLY)
-                    continue;
+                if(mode == MODE_V1_ONLY) {
+                    info.v1_size = v1_size;
+// the size may shrink even before optimizations if the input is short:
+                    info.v1_size = quantize(s, h, pict, 1, &info, ENC_UNCERTAIN);
+                    if(info.v1_size < v1_size)
+// too few eligible blocks, no sense in trying bigger sizes
+                        v1enough = 1;
+
+                    info.v4_size = 0;
+                } else { // mode != MODE_V1_ONLY
+                    // if v4 codebook is empty then only allow V1-only mode
+                    if(!v4_size)
+                        continue;
+
+                    if(mode == MODE_V1_V4) {
+                        info.v4_size = v4_size;
+                        info.v4_size = quantize(s, h, pict, 0, &info, ENC_UNCERTAIN);
+                        if(info.v4_size < v4_size)
+// too few eligible blocks, no sense in trying bigger sizes
+                            v4enough = 1;
+                    }
+                }
 
-                info.v4_codebook = v4 >= 0 ? v4_codebooks[v4] : NULL;
-                score = calculate_mode_score(s, mode, h, v1_size, v4_size, v4, &info);
+                info.mode = mode;
+// choose the best encoding per block, based on current experience
+                score = calculate_mode_score(s, h, &info, 0,
+                                             &v1shrunk, &v4shrunk
+#ifdef CINEPAK_REPORT_SERR
+, &serr
+#endif
+);
+
+                if(mode != MODE_V1_ONLY){
+// recompute the codebooks, omitting the extra blocks
+// we assume we _may_ come here with more blocks to encode than before
+                    info.v1_size = v1_size;
+                    new_v1_size = quantize(s, h, pict, 1, &info, ENC_V1);
+                    if(new_v1_size < info.v1_size){
+                        //av_log(s->avctx, AV_LOG_INFO, "mode %i, %3i, %3i: cut v1 codebook to %i entries\n", mode, v1_size, v4_size, new_v1_size);
+                        info.v1_size = new_v1_size;
+                    }
+// we assume we _may_ come here with more blocks to encode than before
+                    info.v4_size = v4_size;
+                    new_v4_size = quantize(s, h, pict, 0, &info, ENC_V4);
+                    if(new_v4_size < info.v4_size) {
+                        //av_log(s->avctx, AV_LOG_INFO, "mode %i, %3i, %3i: cut v4 codebook to %i entries at first iteration\n", mode, v1_size, v4_size, new_v4_size);
+                        info.v4_size = new_v4_size;
+                    }
+// calculate the resulting score
+// (do not move blocks to codebook encodings now, as some blocks may have
+// got bigger errors despite a smaller training set - but we do not
+// ever grow the training sets back)
+                    for(;;) {
+                        score = calculate_mode_score(s, h, &info, 1,
+                                                     &v1shrunk, &v4shrunk
+#ifdef CINEPAK_REPORT_SERR
+, &serr
+#endif
+);
+// do we have a reason to reiterate?
+                        if(!v1shrunk && !v4shrunk) break;
+// recompute the codebooks, omitting the extra blocks
+                        if(v1shrunk) {
+                            info.v1_size = v1_size;
+                            new_v1_size = quantize(s, h, pict, 1, &info, ENC_V1);
+                            if(new_v1_size < info.v1_size){
+                                //av_log(s->avctx, AV_LOG_INFO, "mode %i, %3i, %3i: cut v1 codebook to %i entries\n", mode, v1_size, v4_size, new_v1_size);
+                                info.v1_size = new_v1_size;
+                            }
+                        }
+                        if(v4shrunk) {
+                            info.v4_size = v4_size;
+                            new_v4_size = quantize(s, h, pict, 0, &info, ENC_V4);
+                            if(new_v4_size < info.v4_size) {
+                                //av_log(s->avctx, AV_LOG_INFO, "mode %i, %3i, %3i: cut v4 codebook to %i entries\n", mode, v1_size, v4_size, new_v4_size);
+                                info.v4_size = new_v4_size;
+                            }
+                        }
+                    }
+                }
 
-                //av_log(s->avctx, AV_LOG_INFO, "%3i %3i score = %li\n", v1_size, v4_size, score);
+                //av_log(s->avctx, AV_LOG_INFO, "%3i %3i score = %lli\n", v1_size, v4_size, (long long int)score);
 
                 if(best_size == 0 || score < *best_score) {
+
                     *best_score = score;
-                    best_size = encode_mode(s, mode, h, v1_size, v4_size, v4, scratch_pict, &info, s->strip_buf + STRIP_HEADER_SIZE);
-                    best_mode = mode;
+#ifdef CINEPAK_REPORT_SERR
+                    *best_serr = serr;
+#endif
+                    best_size = encode_mode(s, h, scratch_pict, last_pict, &info, s->strip_buf + STRIP_HEADER_SIZE);
 
-                    av_log(s->avctx, AV_LOG_INFO, "mode %i, %3i, %3i: %18li %i B\n", mode, v1_size, v4_size, score, best_size);
+                    //av_log(s->avctx, AV_LOG_INFO, "mode %i, %3i, %3i: %18lli %i B", mode, info.v1_size, info.v4_size, (long long int)score, best_size);
+                    //av_log(s->avctx, AV_LOG_INFO, "\n");
+#ifdef CINEPAK_REPORT_SERR
+                    av_log(s->avctx, AV_LOG_INFO, "mode %i, %3i, %3i: %18lli %i B\n", mode, v1_size, v4_size, (long long int)serr, best_size);
+#endif
 
 #ifdef CINEPAKENC_DEBUG
                     //save MB encoding choices
@@ -678,6 +1009,7 @@ static int rd_strip(CinepakEncContext *s, int y, int h, int keyframe, AVPicture
 
                     //memcpy(strip_temp + STRIP_HEADER_SIZE, strip_temp, best_size);
                     write_strip_header(s, y, h, keyframe, s->strip_buf, best_size);
+
                 }
             }
         }
@@ -685,11 +1017,11 @@ static int rd_strip(CinepakEncContext *s, int y, int h, int keyframe, AVPicture
 
 #ifdef CINEPAKENC_DEBUG
     //gather stats. this will only work properly of MAX_STRIPS == 1
-    if(best_mode == MODE_V1_ONLY) {
+    if(best_info.mode == MODE_V1_ONLY) {
         s->num_v1_mode++;
         s->num_v1_encs += s->w*h/MB_AREA;
     } else {
-        if(best_mode == MODE_V1_V4)
+        if(best_info.mode == MODE_V1_V4)
             s->num_v4_mode++;
         else
             s->num_mc_mode++;
@@ -708,13 +1040,12 @@ static int rd_strip(CinepakEncContext *s, int y, int h, int keyframe, AVPicture
     best_size += STRIP_HEADER_SIZE;
     memcpy(buf, s->strip_buf, best_size);
 
-
     return best_size;
 }
 
-static int write_cvid_header(CinepakEncContext *s, unsigned char *buf, int num_strips, int data_size)
+static int write_cvid_header(CinepakEncContext *s, unsigned char *buf, int num_strips, int data_size, int isakeyframe)
 {
-    buf[0] = 0;
+    buf[0] = isakeyframe ? 0 : 1;
     AV_WB24(&buf[1], data_size + CVID_HEADER_SIZE);
     AV_WB16(&buf[4], s->w);
     AV_WB16(&buf[6], s->h);
@@ -723,67 +1054,175 @@ static int write_cvid_header(CinepakEncContext *s, unsigned char *buf, int num_s
     return CVID_HEADER_SIZE;
 }
 
-static int rd_frame(CinepakEncContext *s, AVFrame *frame, unsigned char *buf, int buf_size)
+static int rd_frame(CinepakEncContext *s, AVFrame *frame, int isakeyframe, unsigned char *buf, int buf_size)
 {
-    int num_strips, strip, h, i, y, size, temp_size, best_size;
+    int num_strips, strip, i, y, nexty, size, temp_size, best_size;
     AVPicture last_pict, pict, scratch_pict;
     int64_t best_score = 0, score, score_temp;
+#ifdef CINEPAK_REPORT_SERR
+    int64_t best_serr = 0, serr, serr_temp;
+#endif
 
-    //TODO: support encoding zero strips (meaning skip the whole frame)
-    for(num_strips = MIN_STRIPS; num_strips <= MAX_STRIPS && num_strips <= s->h / MB_SIZE; num_strips++) {
+    int best_nstrips;
+
+    if(s->pix_fmt == AV_PIX_FMT_RGB24) {
+        int x;
+// build a copy of the given frame in the correct colorspace
+        for(y = 0; y < s->h; y += 2) {
+            for(x = 0; x < s->w; x += 2) {
+                uint8_t *ir[2]; int32_t r, g, b, rr, gg, bb;
+                ir[0] = ((AVPicture*)frame)->data[0] + x*3 + y*((AVPicture*)frame)->linesize[0];
+                ir[1] = ir[0] + ((AVPicture*)frame)->linesize[0];
+                get_sub_picture(s, x, y, (AVPicture*)s->input_frame, &scratch_pict);
+                r = g = b = 0;
+                for(i=0; i<4; ++i) {
+                    int i1, i2;
+                    i1 = (i&1); i2 = (i>=2);
+                    rr = ir[i2][i1*3+0];
+                    gg = ir[i2][i1*3+1];
+                    bb = ir[i2][i1*3+2];
+                    r += rr; g += gg; b += bb;
+// using fixed point arithmetic for portable repeatability, scaling by 2^23
+// "Y"
+//                    rr = 0.2857*rr + 0.5714*gg + 0.1429*bb;
+                    rr = (2396625*rr + 4793251*gg + 1198732*bb) >> 23;
+                    if(      rr <   0) rr =   0;
+                    else if (rr > 255) rr = 255;
+                    scratch_pict.data[0][i1 + i2*scratch_pict.linesize[0]] = rr;
+                }
+// let us scale down as late as possible
+//                r /= 4; g /= 4; b /= 4;
+// "U"
+//                rr = -0.1429*r - 0.2857*g + 0.4286*b;
+                rr = (-299683*r - 599156*g + 898839*b) >> 23;
+                if(      rr < -128) rr = -128;
+                else if (rr >  127) rr =  127;
+                scratch_pict.data[1][0] = rr + 128; // quantize needs unsigned
+// "V"
+//                rr = 0.3571*r - 0.2857*g - 0.0714*b;
+                rr = (748893*r - 599156*g - 149737*b) >> 23;
+                if(      rr < -128) rr = -128;
+                else if (rr >  127) rr =  127;
+                scratch_pict.data[2][0] = rr + 128; // quantize needs unsigned
+            }
+        }
+    }
+
+    //would be nice but quite certainly incompatible with vintage players:
+    // support encoding zero strips (meaning skip the whole frame)
+    for(num_strips = s->min_strips; num_strips <= s->max_strips && num_strips <= s->h / MB_SIZE; num_strips++) {
         score = 0;
         size = 0;
-        h = s->h / num_strips;
-        //make h into next multiple of 4
-        h += 4 - (h & 3);
+#ifdef CINEPAK_REPORT_SERR
+        serr = 0;
+#endif
+
+        for(y = 0, strip = 1; y < s->h; strip++, y = nexty) {
+            int strip_height;
 
-        for(strip = 0; strip < num_strips; strip++) {
-            y = strip*h;
+            nexty = strip * s->h / num_strips; // <= s->h
+            //make nexty the next multiple of 4 if not already there
+            if(nexty & 3)
+                nexty += 4 - (nexty & 3);
 
-            get_sub_picture(s, 0, y, (AVPicture*)frame,            &pict);
-            get_sub_picture(s, 0, y, (AVPicture*)&s->last_frame,    &last_pict);
-            get_sub_picture(s, 0, y, (AVPicture*)&s->scratch_frame, &scratch_pict);
+            strip_height = nexty - y;
+            if(strip_height <= 0) { // can this ever happen?
+                av_log(s->avctx, AV_LOG_INFO, "skipping zero height strip %i of %i\n", strip, num_strips);
+                continue;
+            }
+
+            if(s->pix_fmt == AV_PIX_FMT_RGB24)
+                get_sub_picture(s, 0, y, (AVPicture*)s->input_frame,    &pict);
+            else
+                get_sub_picture(s, 0, y, (AVPicture*)frame,              &pict);
+            get_sub_picture(s, 0, y, (AVPicture*)s->last_frame,    &last_pict);
+            get_sub_picture(s, 0, y, (AVPicture*)s->scratch_frame, &scratch_pict);
 
-            if((temp_size = rd_strip(s, y, FFMIN(h, s->h - y), frame->key_frame, &last_pict, &pict, &scratch_pict, s->frame_buf + CVID_HEADER_SIZE, &score_temp)) < 0)
+            if((temp_size = rd_strip(s, y, strip_height, isakeyframe, &last_pict, &pict, &scratch_pict, s->frame_buf + size + CVID_HEADER_SIZE, &score_temp
+#ifdef CINEPAK_REPORT_SERR
+, &serr_temp
+#endif
+)) < 0)
                 return temp_size;
 
             score += score_temp;
+#ifdef CINEPAK_REPORT_SERR
+            serr += serr_temp;
+#endif
             size += temp_size;
+            //av_log(s->avctx, AV_LOG_INFO, "strip %d, isakeyframe=%d", strip, isakeyframe);
+            //av_log(s->avctx, AV_LOG_INFO, "\n");
         }
 
         if(best_score == 0 || score < best_score) {
             best_score = score;
-            best_size = size + write_cvid_header(s, s->frame_buf, num_strips, size);
-            av_log(s->avctx, AV_LOG_INFO, "best number of strips so far: %2i, %12li, %i B\n", num_strips, score, best_size);
+#ifdef CINEPAK_REPORT_SERR
+            best_serr = serr;
+#endif
+            best_size = size + write_cvid_header(s, s->frame_buf, num_strips, size, isakeyframe);
+            //av_log(s->avctx, AV_LOG_INFO, "best number of strips so far: %2i, %12lli, %i B\n", num_strips, (long long int)score, best_size);
+#ifdef CINEPAK_REPORT_SERR
+            av_log(s->avctx, AV_LOG_INFO, "best number of strips so far: %2i, %12lli, %i B\n", num_strips, (long long int)serr, best_size);
+#endif
 
-            FFSWAP(AVFrame, s->best_frame, s->scratch_frame);
+            FFSWAP(AVFrame *, s->best_frame, s->scratch_frame);
+            memcpy(buf, s->frame_buf, best_size);
+            best_nstrips = num_strips;
         }
+// avoid trying too many strip numbers without a real reason
+// (this makes the processing of the very first frame faster)
+        if(num_strips - best_nstrips > 4)
+            break;
     }
 
-    memcpy(buf, s->frame_buf, best_size);
+// let the number of strips slowly adapt to the changes in the contents,
+// compared to full bruteforcing every time this will occasionally lead
+// to some r/d performance loss but makes encoding up to several times faster
+#ifdef CINEPAK_AGGRESSIVE_STRIP_NUMBER_ADAPTIVITY
+    s->max_strips = best_nstrips + 4;
+    if(s->max_strips >= MAX_STRIPS)
+        s->max_strips = MAX_STRIPS;
+    s->min_strips = best_nstrips - 4;
+    if(s->min_strips < MIN_STRIPS)
+        s->min_strips = MIN_STRIPS;
+#else
+    if(best_nstrips == s->max_strips) { // let us try to step up
+        s->max_strips = best_nstrips + 1;
+        if(s->max_strips >= MAX_STRIPS)
+            s->max_strips = MAX_STRIPS;
+    } else { // try to step down
+        s->max_strips = best_nstrips;
+    }
+    s->min_strips = s->max_strips - 1;
+    if(s->min_strips < MIN_STRIPS)
+        s->min_strips = MIN_STRIPS;
+#endif
 
     return best_size;
 }
 
-static int cinepak_encode_frame(AVCodecContext *avctx, unsigned char *buf, int buf_size, void *data)
+static int cinepak_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
+                                const AVFrame *frame, int *got_packet)
 {
     CinepakEncContext *s = avctx->priv_data;
-    AVFrame *frame = data;
     int ret;
 
     s->lambda = frame->quality ? frame->quality - 1 : 2 * FF_LAMBDA_SCALE;
 
-    frame->key_frame = s->curframe == 0;
-    frame->pict_type = frame->key_frame ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
+    if ((ret = ff_alloc_packet(pkt, s->frame_buf_size)) < 0)
+        return ret;
+    ret = rd_frame(s, frame, (s->curframe == 0), pkt->data, s->frame_buf_size);
+    pkt->size = ret;
+    if (s->curframe == 0)
+        pkt->flags |= AV_PKT_FLAG_KEY;
+    *got_packet = 1;
 
-    ret = rd_frame(s, frame, buf, buf_size);
-
-    FFSWAP(AVFrame, s->last_frame, s->best_frame);
+    FFSWAP(AVFrame *, s->last_frame, s->best_frame);
 
     if (++s->curframe >= s->keyint)
         s->curframe = 0;
 
-    return ret;
+    return 0;
 }
 
 static av_cold int cinepak_encode_end(AVCodecContext *avctx)
@@ -791,20 +1230,27 @@ static av_cold int cinepak_encode_end(AVCodecContext *avctx)
     CinepakEncContext *s = avctx->priv_data;
     int x;
 
-    av_free(s->codebook_input);
-    av_free(s->codebook_closest);
-    av_free(s->strip_buf);
-    av_free(s->frame_buf);
-    av_free(s->mb);
+    av_frame_free(&s->last_frame);
+    av_frame_free(&s->best_frame);
+    av_frame_free(&s->scratch_frame);
+    if (avctx->pix_fmt == AV_PIX_FMT_RGB24)
+        av_frame_free(&s->input_frame);
+    av_freep(&s->codebook_input);
+    av_freep(&s->codebook_closest);
+    av_freep(&s->strip_buf);
+    av_freep(&s->frame_buf);
+    av_freep(&s->mb);
 #ifdef CINEPAKENC_DEBUG
-    av_free(s->best_mb);
+    av_freep(&s->best_mb);
 #endif
 
-    for(x = 0; x < 3; x++)
-        av_free(s->pict_bufs[x]);
+    for(x = 0; x < (avctx->pix_fmt == AV_PIX_FMT_RGB24 ? 4 : 3); x++)
+        av_freep(&s->pict_bufs[x]);
 
+#ifdef CINEPAKENC_DEBUG
     av_log(avctx, AV_LOG_INFO, "strip coding stats: %i V1 mode, %i V4 mode, %i MC mode (%i V1 encs, %i V4 encs, %i skips)\n",
         s->num_v1_mode, s->num_v4_mode, s->num_mc_mode, s->num_v1_encs, s->num_v4_encs, s->num_skips);
+#endif
 
     return 0;
 }