avcodec: Implement mpeg4 nvdec hwaccel

This was predictably nightmarish, given how ridiculous mpeg4 is.
I had to stare at the cuvid parser output for a long time to work
out what each field was supposed to be, and even then, I still don't
fully understand some of them. Particularly:

vop_coded: If I'm reading the decoder correctly, this flag will always
           be 1 as the decoder will not pass the hwaccel any frame
           where it is not 1.
divx_flags: There's obviously no documentation on what the possible
            flags are. I simply observed that this is '0' for a
            normal bitstream and '5' for packed b-frames.
gmc_enabled: I had a number of guesses as to what this mapped to.
             I picked the condition I did based on when the cuvid
             parser was setting flag.

Also note that as with the vdpau hwaccel, the decoder needs to
consume the entire frame and not the slice.

6 files changed, 128 insertions, 1 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 0573454c7b..2af957ab72 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -861,6 +861,7 @@ OBJS-$(CONFIG_MPEG2_VAAPI_HWACCEL)        += vaapi_mpeg2.o
 OBJS-$(CONFIG_MPEG2_VDPAU_HWACCEL)        += vdpau_mpeg12.o
 OBJS-$(CONFIG_MPEG2_VIDEOTOOLBOX_HWACCEL) += videotoolbox.o
 OBJS-$(CONFIG_MPEG2_XVMC_HWACCEL)         += mpegvideo_xvmc.o
+OBJS-$(CONFIG_MPEG4_NVDEC_HWACCEL)        += nvdec_mpeg4.o
 OBJS-$(CONFIG_MPEG4_VAAPI_HWACCEL)        += vaapi_mpeg4.o
 OBJS-$(CONFIG_MPEG4_VDPAU_HWACCEL)        += vdpau_mpeg4.o
 OBJS-$(CONFIG_MPEG4_VIDEOTOOLBOX_HWACCEL) += videotoolbox.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index e9df7049de..85c38c83aa 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -106,6 +106,7 @@ static void register_all(void)
     REGISTER_HWACCEL(MPEG4_CUVID,       mpeg4_cuvid);
     REGISTER_HWACCEL(MPEG4_MEDIACODEC,  mpeg4_mediacodec);
     REGISTER_HWACCEL(MPEG4_MMAL,        mpeg4_mmal);
+    REGISTER_HWACCEL(MPEG4_NVDEC,       mpeg4_nvdec);
     REGISTER_HWACCEL(MPEG4_VAAPI,       mpeg4_vaapi);
     REGISTER_HWACCEL(MPEG4_VDPAU,       mpeg4_vdpau);
     REGISTER_HWACCEL(MPEG4_VIDEOTOOLBOX, mpeg4_videotoolbox);
diff --git a/libavcodec/h263dec.c b/libavcodec/h263dec.c
index c7cf4bc0c2..b222de793b 100644
--- a/libavcodec/h263dec.c
+++ b/libavcodec/h263dec.c
@@ -714,6 +714,9 @@ const enum AVPixelFormat ff_h263_hwaccel_pixfmt_list_420[] = {
 #if CONFIG_H263_VAAPI_HWACCEL || CONFIG_MPEG4_VAAPI_HWACCEL
     AV_PIX_FMT_VAAPI,
 #endif
+#if CONFIG_MPEG4_NVDEC_HWACCEL
+    AV_PIX_FMT_CUDA,
+#endif
 #if CONFIG_MPEG4_VDPAU_HWACCEL
     AV_PIX_FMT_VDPAU,
 #endif
diff --git a/libavcodec/nvdec.c b/libavcodec/nvdec.c
index d5cf1058cb..efcd47a7f7 100644
--- a/libavcodec/nvdec.c
+++ b/libavcodec/nvdec.c
@@ -56,6 +56,7 @@ static int map_avcodec_id(enum AVCodecID id)
     case AV_CODEC_ID_HEVC:       return cudaVideoCodec_HEVC;
     case AV_CODEC_ID_MPEG1VIDEO: return cudaVideoCodec_MPEG1;
     case AV_CODEC_ID_MPEG2VIDEO: return cudaVideoCodec_MPEG2;
+    case AV_CODEC_ID_MPEG4:      return cudaVideoCodec_MPEG4;
     case AV_CODEC_ID_VC1:        return cudaVideoCodec_VC1;
     case AV_CODEC_ID_VP9:        return cudaVideoCodec_VP9;
     case AV_CODEC_ID_WMV3:       return cudaVideoCodec_VC1;
diff --git a/libavcodec/nvdec_mpeg4.c b/libavcodec/nvdec_mpeg4.c
new file mode 100644
index 0000000000..a0f9280ea2
--- /dev/null
+++ b/libavcodec/nvdec_mpeg4.c
@@ -0,0 +1,121 @@
+/*
+ * MPEG-4 Part 2 HW decode acceleration through NVDEC
+ *
+ * Copyright (c) 2017 Philip Langdale
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avcodec.h"
+#include "mpeg4video.h"
+#include "nvdec.h"
+#include "decode.h"
+
+static int nvdec_mpeg4_start_frame(AVCodecContext *avctx, const uint8_t *buffer, uint32_t size)
+{
+    Mpeg4DecContext *m = avctx->priv_data;
+    MpegEncContext *s = &m->m;
+
+    NVDECContext      *ctx = avctx->internal->hwaccel_priv_data;
+    CUVIDPICPARAMS     *pp = &ctx->pic_params;
+    CUVIDMPEG4PICPARAMS *ppc = &pp->CodecSpecific.mpeg4;
+    FrameDecodeData *fdd;
+    NVDECFrame *cf;
+    AVFrame *cur_frame = s->current_picture.f;
+
+    int ret, i;
+
+    ret = ff_nvdec_start_frame(avctx, cur_frame);
+    if (ret < 0)
+        return ret;
+
+    fdd = (FrameDecodeData*)cur_frame->private_ref->data;
+    cf  = (NVDECFrame*)fdd->hwaccel_priv;
+
+    *pp = (CUVIDPICPARAMS) {
+        .PicWidthInMbs     = (cur_frame->width  + 15) / 16,
+        .FrameHeightInMbs  = (cur_frame->height + 15) / 16,
+        .CurrPicIdx        = cf->idx,
+
+        .intra_pic_flag    = s->pict_type == AV_PICTURE_TYPE_I,
+        .ref_pic_flag      = s->pict_type == AV_PICTURE_TYPE_I ||
+                             s->pict_type == AV_PICTURE_TYPE_P ||
+                             s->pict_type == AV_PICTURE_TYPE_S,
+
+        .CodecSpecific.mpeg4 = {
+            .ForwardRefIdx                = ff_nvdec_get_ref_idx(s->last_picture.f),
+            .BackwardRefIdx               = ff_nvdec_get_ref_idx(s->next_picture.f),
+
+            .video_object_layer_width     = s->width,
+            .video_object_layer_height    = s->height,
+            .vop_time_increment_bitcount  = m->time_increment_bits,
+            .top_field_first              = s->top_field_first,
+            .resync_marker_disable        = !m->resync_marker,
+            .quant_type                   = s->mpeg_quant,
+            .quarter_sample               = s->quarter_sample,
+            .short_video_header           = avctx->codec->id == AV_CODEC_ID_H263,
+            .divx_flags                   = s->divx_packed ? 5 : 0,
+
+            .vop_coding_type              = s->pict_type - AV_PICTURE_TYPE_I,
+            .vop_coded                    = 1,
+            .vop_rounding_type            = s->no_rounding,
+            .alternate_vertical_scan_flag = s->alternate_scan,
+            .interlaced                   = !s->progressive_sequence,
+            .vop_fcode_forward            = s->f_code,
+            .vop_fcode_backward           = s->b_code,
+            .trd                          = { s->pp_time, s->pp_field_time >> 1 },
+            .trb                          = { s->pb_time, s->pb_field_time >> 1 },
+
+            .gmc_enabled                  = s->pict_type == AV_PICTURE_TYPE_S &&
+                                            m->vol_sprite_usage == GMC_SPRITE,
+        }
+    };
+
+    for (i = 0; i < 64; ++i) {
+        ppc->QuantMatrixIntra[i] = s->intra_matrix[i];
+        ppc->QuantMatrixInter[i] = s->inter_matrix[i];
+    }
+
+    // We need to pass the full frame buffer and not just the slice
+    return ff_nvdec_simple_decode_slice(avctx, buffer, size);
+}
+
+static int nvdec_mpeg4_decode_slice(AVCodecContext *avctx, const uint8_t *buffer, uint32_t size)
+{
+    return 0;
+}
+
+static int nvdec_mpeg4_frame_params(AVCodecContext *avctx,
+                                  AVBufferRef *hw_frames_ctx)
+{
+    // Each frame can at most have one P and one B reference
+    return ff_nvdec_frame_params(avctx, hw_frames_ctx, 2);
+}
+
+AVHWAccel ff_mpeg4_nvdec_hwaccel = {
+    .name                 = "mpeg4_nvdec",
+    .type                 = AVMEDIA_TYPE_VIDEO,
+    .id                   = AV_CODEC_ID_MPEG4,
+    .pix_fmt              = AV_PIX_FMT_CUDA,
+    .start_frame          = nvdec_mpeg4_start_frame,
+    .end_frame            = ff_nvdec_simple_end_frame,
+    .decode_slice         = nvdec_mpeg4_decode_slice,
+    .frame_params         = nvdec_mpeg4_frame_params,
+    .init                 = ff_nvdec_decode_init,
+    .uninit               = ff_nvdec_decode_uninit,
+    .priv_data_size       = sizeof(NVDECContext),
+};
diff --git a/libavcodec/version.h b/libavcodec/version.h
index ff54670ea9..c8550bca9a 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,7 +29,7 @@
 
 #define LIBAVCODEC_VERSION_MAJOR  58
 #define LIBAVCODEC_VERSION_MINOR   3
-#define LIBAVCODEC_VERSION_MICRO 104
+#define LIBAVCODEC_VERSION_MICRO 105
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \