lavf: replace AVStream.codec with AVStream.codecpar

Currently, AVStream contains an embedded AVCodecContext instance, which
is used by demuxers to export stream parameters to the caller and by
muxers to receive stream parameters from the caller. It is also used
internally as the codec context that is passed to parsers.

In addition, it is also widely used by the callers as the decoding (when
demuxer) or encoding (when muxing) context, though this has been
officially discouraged since Libav 11.

There are multiple important problems with this approach:
    - the fields in AVCodecContext are in general one of
        * stream parameters
        * codec options
        * codec state
      However, it's not clear which ones are which. It is consequently
      unclear which fields are a demuxer allowed to set or a muxer allowed to
      read. This leads to erratic behaviour depending on whether decoding or
      encoding is being performed or not (and whether it uses the AVStream
      embedded codec context).
    - various synchronization issues arising from the fact that the same
      context is used by several different APIs (muxers/demuxers,
      parsers, bitstream filters and encoders/decoders) simultaneously, with
      there being no clear rules for who can modify what and the different
      processes being typically delayed with respect to each other.
    - avformat_find_stream_info() making it necessary to support opening
      and closing a single codec context multiple times, thus
      complicating the semantics of freeing various allocated objects in the
      codec context.

Those problems are resolved by replacing the AVStream embedded codec
context with a newly added AVCodecParameters instance, which stores only
the stream parameters exported by the demuxers or read by the muxers.

1 files changed, 67 insertions, 68 deletions

diff --git a/libavformat/avidec.c b/libavformat/avidec.c
index 4cebd17919..f5705e5436 100644
--- a/libavformat/avidec.c
+++ b/libavformat/avidec.c
@@ -487,8 +487,8 @@ static int avi_read_header(AVFormatContext *s)
                     goto fail;
 
                 ast = s->streams[0]->priv_data;
-                av_freep(&s->streams[0]->codec->extradata);
-                av_freep(&s->streams[0]->codec);
+                av_freep(&s->streams[0]->codecpar->extradata);
+                av_freep(&s->streams[0]->codecpar);
                 av_freep(&s->streams[0]->info);
                 av_freep(&s->streams[0]);
                 s->nb_streams = 0;
@@ -606,10 +606,10 @@ static int avi_read_header(AVFormatContext *s)
                 switch (codec_type) {
                 case AVMEDIA_TYPE_VIDEO:
                     if (amv_file_format) {
-                        st->codec->width      = avih_width;
-                        st->codec->height     = avih_height;
-                        st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
-                        st->codec->codec_id   = AV_CODEC_ID_AMV;
+                        st->codecpar->width      = avih_width;
+                        st->codecpar->height     = avih_height;
+                        st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
+                        st->codecpar->codec_id   = AV_CODEC_ID_AMV;
                         avio_skip(pb, size);
                         break;
                     }
@@ -617,41 +617,41 @@ static int avi_read_header(AVFormatContext *s)
 
                     if (tag1 == MKTAG('D', 'X', 'S', 'B') ||
                         tag1 == MKTAG('D', 'X', 'S', 'A')) {
-                        st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
-                        st->codec->codec_tag  = tag1;
-                        st->codec->codec_id   = AV_CODEC_ID_XSUB;
+                        st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
+                        st->codecpar->codec_tag  = tag1;
+                        st->codecpar->codec_id   = AV_CODEC_ID_XSUB;
                         break;
                     }
 
                     if (size > 10 * 4 && size < (1 << 30)) {
-                        st->codec->extradata_size = size - 10 * 4;
-                        st->codec->extradata      = av_malloc(st->codec->extradata_size +
-                                                              AV_INPUT_BUFFER_PADDING_SIZE);
-                        if (!st->codec->extradata) {
-                            st->codec->extradata_size = 0;
+                        st->codecpar->extradata_size = size - 10 * 4;
+                        st->codecpar->extradata      = av_malloc(st->codecpar->extradata_size +
+                                                                 AV_INPUT_BUFFER_PADDING_SIZE);
+                        if (!st->codecpar->extradata) {
+                            st->codecpar->extradata_size = 0;
                             return AVERROR(ENOMEM);
                         }
                         avio_read(pb,
-                                  st->codec->extradata,
-                                  st->codec->extradata_size);
+                                  st->codecpar->extradata,
+                                  st->codecpar->extradata_size);
                     }
 
                     // FIXME: check if the encoder really did this correctly
-                    if (st->codec->extradata_size & 1)
+                    if (st->codecpar->extradata_size & 1)
                         avio_r8(pb);
 
                     /* Extract palette from extradata if bpp <= 8.
                      * This code assumes that extradata contains only palette.
                      * This is true for all paletted codecs implemented in
                      * Libav. */
-                    if (st->codec->extradata_size &&
-                        (st->codec->bits_per_coded_sample <= 8)) {
-                        int pal_size = (1 << st->codec->bits_per_coded_sample) << 2;
+                    if (st->codecpar->extradata_size &&
+                        (st->codecpar->bits_per_coded_sample <= 8)) {
+                        int pal_size = (1 << st->codecpar->bits_per_coded_sample) << 2;
                         const uint8_t *pal_src;
 
-                        pal_size = FFMIN(pal_size, st->codec->extradata_size);
-                        pal_src  = st->codec->extradata +
-                                   st->codec->extradata_size - pal_size;
+                        pal_size = FFMIN(pal_size, st->codecpar->extradata_size);
+                        pal_src  = st->codecpar->extradata +
+                                   st->codecpar->extradata_size - pal_size;
 #if HAVE_BIGENDIAN
                         for (i = 0; i < pal_size / 4; i++)
                             ast->pal[i] = av_bswap32(((uint32_t *)pal_src)[i]);
@@ -663,17 +663,17 @@ static int avi_read_header(AVFormatContext *s)
 
                     print_tag("video", tag1, 0);
 
-                    st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
-                    st->codec->codec_tag  = tag1;
-                    st->codec->codec_id   = ff_codec_get_id(ff_codec_bmp_tags,
+                    st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
+                    st->codecpar->codec_tag  = tag1;
+                    st->codecpar->codec_id   = ff_codec_get_id(ff_codec_bmp_tags,
                                                             tag1);
                     /* If codec is not found yet, try with the mov tags. */
-                    if (!st->codec->codec_id) {
+                    if (!st->codecpar->codec_id) {
                         char tag_buf[32];
                         av_get_codec_tag_string(tag_buf, sizeof(tag_buf), tag1);
-                        st->codec->codec_id =
+                        st->codecpar->codec_id =
                             ff_codec_get_id(ff_codec_movvideo_tags, tag1);
-                        if (st->codec->codec_id)
+                        if (st->codecpar->codec_id)
                            av_log(s, AV_LOG_WARNING,
                                   "mov tag found in avi (fourcc %s)\n",
                                   tag_buf);
@@ -682,45 +682,45 @@ static int avi_read_header(AVFormatContext *s)
                      * for generating correct pts. */
                     st->need_parsing = AVSTREAM_PARSE_HEADERS;
 
-                    if (st->codec->codec_id == AV_CODEC_ID_MPEG4 &&
+                    if (st->codecpar->codec_id == AV_CODEC_ID_MPEG4 &&
                         ast->handler == MKTAG('X', 'V', 'I', 'D'))
-                        st->codec->codec_tag = MKTAG('X', 'V', 'I', 'D');
+                        st->codecpar->codec_tag = MKTAG('X', 'V', 'I', 'D');
 
                     // Support "Resolution 1:1" for Avid AVI Codec
                     if (tag1 == MKTAG('A', 'V', 'R', 'n') &&
-                        st->codec->extradata_size >= 31   &&
-                        !memcmp(&st->codec->extradata[28], "1:1", 3))
-                        st->codec->codec_id = AV_CODEC_ID_RAWVIDEO;
-
-                    if (st->codec->codec_tag == 0 && st->codec->height > 0 &&
-                        st->codec->extradata_size < 1U << 30) {
-                        st->codec->extradata_size += 9;
-                        if ((ret = av_reallocp(&st->codec->extradata,
-                                               st->codec->extradata_size +
+                        st->codecpar->extradata_size >= 31   &&
+                        !memcmp(&st->codecpar->extradata[28], "1:1", 3))
+                        st->codecpar->codec_id = AV_CODEC_ID_RAWVIDEO;
+
+                    if (st->codecpar->codec_tag == 0 && st->codecpar->height > 0 &&
+                        st->codecpar->extradata_size < 1U << 30) {
+                        st->codecpar->extradata_size += 9;
+                        if ((ret = av_reallocp(&st->codecpar->extradata,
+                                               st->codecpar->extradata_size +
                                                AV_INPUT_BUFFER_PADDING_SIZE)) < 0) {
-                            st->codec->extradata_size = 0;
+                            st->codecpar->extradata_size = 0;
                             return ret;
                         } else
-                            memcpy(st->codec->extradata + st->codec->extradata_size - 9,
+                            memcpy(st->codecpar->extradata + st->codecpar->extradata_size - 9,
                                    "BottomUp", 9);
                     }
-                    st->codec->height = FFABS(st->codec->height);
+                    st->codecpar->height = FFABS(st->codecpar->height);
 
 //                    avio_skip(pb, size - 5 * 4);
                     break;
                 case AVMEDIA_TYPE_AUDIO:
-                    ret = ff_get_wav_header(s, pb, st->codec, size);
+                    ret = ff_get_wav_header(s, pb, st->codecpar, size);
                     if (ret < 0)
                         return ret;
-                    ast->dshow_block_align = st->codec->block_align;
-                    if (ast->sample_size && st->codec->block_align &&
-                        ast->sample_size != st->codec->block_align) {
+                    ast->dshow_block_align = st->codecpar->block_align;
+                    if (ast->sample_size && st->codecpar->block_align &&
+                        ast->sample_size != st->codecpar->block_align) {
                         av_log(s,
                                AV_LOG_WARNING,
                                "sample size (%d) != block align (%d)\n",
                                ast->sample_size,
-                               st->codec->block_align);
-                        ast->sample_size = st->codec->block_align;
+                               st->codecpar->block_align);
+                        ast->sample_size = st->codecpar->block_align;
                     }
                     /* 2-aligned
                      * (fix for Stargate SG-1 - 3x18 - Shades of Grey.avi) */
@@ -732,28 +732,28 @@ static int avi_read_header(AVFormatContext *s)
                     /* ADTS header is in extradata, AAC without header must be
                      * stored as exact frames. Parser not needed and it will
                      * fail. */
-                    if (st->codec->codec_id == AV_CODEC_ID_AAC &&
-                        st->codec->extradata_size)
+                    if (st->codecpar->codec_id == AV_CODEC_ID_AAC &&
+                        st->codecpar->extradata_size)
                         st->need_parsing = AVSTREAM_PARSE_NONE;
                     /* AVI files with Xan DPCM audio (wrongly) declare PCM
                      * audio in the header but have Axan as stream_code_tag. */
                     if (ast->handler == AV_RL32("Axan")) {
-                        st->codec->codec_id  = AV_CODEC_ID_XAN_DPCM;
-                        st->codec->codec_tag = 0;
+                        st->codecpar->codec_id  = AV_CODEC_ID_XAN_DPCM;
+                        st->codecpar->codec_tag = 0;
                     }
                     if (amv_file_format) {
-                        st->codec->codec_id    = AV_CODEC_ID_ADPCM_IMA_AMV;
+                        st->codecpar->codec_id    = AV_CODEC_ID_ADPCM_IMA_AMV;
                         ast->dshow_block_align = 0;
                     }
                     break;
                 case AVMEDIA_TYPE_SUBTITLE:
-                    st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
-                    st->codec->codec_id   = AV_CODEC_ID_PROBE;
+                    st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
+                    st->codecpar->codec_id   = AV_CODEC_ID_PROBE;
                     break;
                 default:
-                    st->codec->codec_type = AVMEDIA_TYPE_DATA;
-                    st->codec->codec_id   = AV_CODEC_ID_NONE;
-                    st->codec->codec_tag  = 0;
+                    st->codecpar->codec_type = AVMEDIA_TYPE_DATA;
+                    st->codecpar->codec_id   = AV_CODEC_ID_NONE;
+                    st->codecpar->codec_tag  = 0;
                     avio_skip(pb, size);
                     break;
                 }
@@ -895,8 +895,7 @@ static int read_gab2_sub(AVStream *st, AVPacket *pkt)
         ast->sub_ctx->pb = pb;
         if (!avformat_open_input(&ast->sub_ctx, "", sub_demuxer, NULL)) {
             ff_read_packet(ast->sub_ctx, &ast->sub_pkt);
-            *st->codec = *ast->sub_ctx->streams[0]->codec;
-            ast->sub_ctx->streams[0]->codec->extradata = NULL;
+            avcodec_parameters_copy(st->codecpar, ast->sub_ctx->streams[0]->codecpar);
             time_base = ast->sub_ctx->streams[0]->time_base;
             avpriv_set_pts_info(st, 64, time_base.num, time_base.den);
         }
@@ -1022,8 +1021,8 @@ start_sync:
                 AVIStream *ast1 = st1->priv_data;
                 // workaround for broken small-file-bug402.avi
                 if (d[2] == 'w' && d[3] == 'b' && n == 0 &&
-                    st->codec->codec_type  == AVMEDIA_TYPE_VIDEO &&
-                    st1->codec->codec_type == AVMEDIA_TYPE_AUDIO &&
+                    st->codecpar->codec_type  == AVMEDIA_TYPE_VIDEO &&
+                    st1->codecpar->codec_type == AVMEDIA_TYPE_AUDIO &&
                     ast->prefix == 'd' * 256 + 'c' &&
                     (d[2] * 256 + d[3] == ast1->prefix ||
                      !ast1->prefix_count)) {
@@ -1230,8 +1229,8 @@ resync:
             pkt->flags |= AV_PKT_FLAG_KEY;
             if (size < 0)
                 av_packet_unref(pkt);
-        } else if (st->codec->codec_type == AVMEDIA_TYPE_SUBTITLE &&
-                   !st->codec->codec_tag && read_gab2_sub(st, pkt)) {
+        } else if (st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE &&
+                   !st->codecpar->codec_tag && read_gab2_sub(st, pkt)) {
             ast->frame_offset++;
             avi->stream_index = -1;
             ast->remaining    = 0;
@@ -1255,7 +1254,7 @@ resync:
                     size);
             pkt->stream_index = avi->stream_index;
 
-            if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
+            if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
                 AVIndexEntry *e;
                 int index;
                 assert(st->index_entries);
@@ -1391,7 +1390,7 @@ static int check_stream_max_drift(AVFormatContext *s)
                 max_dts = FFMAX(max_dts, dts);
                 max_buffer = FFMAX(max_buffer,
                                    av_rescale(dts - min_dts,
-                                              st->codec->bit_rate,
+                                              st->codecpar->bit_rate,
                                               AV_TIME_BASE));
             }
         }
@@ -1555,7 +1554,7 @@ static int avi_read_seek(AVFormatContext *s, int stream_index,
         if (st2->nb_index_entries <= 0)
             continue;
 
-//        assert(st2->codec->block_align);
+//        assert(st2->codecpar->block_align);
         assert((int64_t)st2->time_base.num * ast2->rate ==
                (int64_t)st2->time_base.den * ast2->scale);
         index = av_index_search_timestamp(st2,