[FFmpeg-devel] [PATCH] libavformat/matroskaenc: Add WebM DASH support
Michael Niedermayer
michaelni at gmx.at
Wed May 7 22:40:39 CEST 2014
On Wed, May 07, 2014 at 09:46:40AM -0700, Vignesh Venkatasubramanian wrote:
> WebM DASH specification [1] requires the Clusters and Cues to be output in a
> specific way. Adding a flag to matroskaenc that will enable support for
> creating WebM/Mkv files conforming to the WebM DASH specification.
>
> [1] http://wiki.webmproject.org/adaptive-streaming/webm-dash-specification
>
> Signed-off-by: Vignesh Venkatasubramanian <vigneshv at google.com>
> ---
> libavformat/matroskaenc.c | 68 ++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 50 insertions(+), 18 deletions(-)
>
> diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
> index e5e6116..3cf6e73 100644
> --- a/libavformat/matroskaenc.c
> +++ b/libavformat/matroskaenc.c
> @@ -70,6 +70,7 @@ typedef struct mkv_seekhead {
>
> typedef struct {
> uint64_t pts;
> + int stream_idx;
> int tracknum;
> int64_t cluster_pos; ///< file offset of the cluster containing the block
> int64_t relative_pos; ///< relative offset from the position of the cluster containing the block
> @@ -114,6 +115,8 @@ typedef struct MatroskaMuxContext {
> int cluster_size_limit;
> int64_t cues_pos;
> int64_t cluster_time_limit;
> + int is_dash;
> + int dash_track_number;
>
> uint32_t chapter_id_offset;
> int wrote_chapters;
> @@ -399,8 +402,8 @@ static mkv_cues * mkv_start_cues(int64_t segment_offset)
> return cues;
> }
>
> -static int mkv_add_cuepoint(mkv_cues *cues, int stream, int64_t ts, int64_t cluster_pos, int64_t relative_pos,
> - int64_t duration)
> +static int mkv_add_cuepoint(mkv_cues *cues, int stream, int tracknum, int64_t ts,
> + int64_t cluster_pos, int64_t relative_pos, int64_t duration)
> {
> mkv_cuepoint *entries = cues->entries;
>
> @@ -413,7 +416,8 @@ static int mkv_add_cuepoint(mkv_cues *cues, int stream, int64_t ts, int64_t clus
> cues->entries = entries;
>
> cues->entries[cues->num_entries].pts = ts;
> - cues->entries[cues->num_entries].tracknum = stream + 1;
> + cues->entries[cues->num_entries].stream_idx = stream;
> + cues->entries[cues->num_entries].tracknum = tracknum;
> cues->entries[cues->num_entries].cluster_pos = cluster_pos - cues->segment_offset;
> cues->entries[cues->num_entries].relative_pos = relative_pos;
> cues->entries[cues->num_entries++].duration = duration;
> @@ -443,7 +447,7 @@ static int64_t mkv_write_cues(AVIOContext *pb, mkv_cues *cues, mkv_track *tracks
> for (j = 0; j < num_tracks; j++)
> tracks[j].has_cue = 0;
> for (j = 0; j < cues->num_entries - i && entry[j].pts == pts; j++) {
> - int tracknum = entry[j].tracknum - 1;
> + int tracknum = entry[j].stream_idx;
> av_assert0(tracknum>=0 && tracknum<num_tracks);
> if (tracks[tracknum].has_cue)
> continue;
> @@ -646,8 +650,10 @@ static int mkv_write_tracks(AVFormatContext *s)
> get_aac_sample_rates(s, codec, &sample_rate, &output_sample_rate);
>
> track = start_ebml_master(pb, MATROSKA_ID_TRACKENTRY, 0);
> - put_ebml_uint (pb, MATROSKA_ID_TRACKNUMBER , i + 1);
> - put_ebml_uint (pb, MATROSKA_ID_TRACKUID , i + 1);
> + put_ebml_uint (pb, MATROSKA_ID_TRACKNUMBER,
> + mkv->is_dash ? mkv->dash_track_number : i + 1);
> + put_ebml_uint (pb, MATROSKA_ID_TRACKUID,
> + mkv->is_dash ? mkv->dash_track_number : i + 1);
> put_ebml_uint (pb, MATROSKA_ID_TRACKFLAGLACING , 0); // no lacing (yet)
>
> if ((tag = av_dict_get(st->metadata, "title", NULL, 0)))
> @@ -1425,7 +1431,8 @@ static void mkv_write_block(AVFormatContext *s, AVIOContext *pb,
>
> put_ebml_id(pb, blockid);
> put_ebml_num(pb, size+4, 0);
> - avio_w8(pb, 0x80 | (pkt->stream_index + 1)); // this assumes stream_index is less than 126
> + // this assumes stream_index is less than 126
> + avio_w8(pb, 0x80 | (mkv->is_dash ? mkv->dash_track_number : (pkt->stream_index + 1)));
> avio_wb16(pb, ts - mkv->cluster_pts);
> avio_w8(pb, flags);
> avio_write(pb, data + offset, size);
> @@ -1539,7 +1546,7 @@ static void mkv_flush_dynbuf(AVFormatContext *s)
> mkv->dyn_bc = NULL;
> }
>
> -static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
> +static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_cue)
> {
> MatroskaMuxContext *mkv = s->priv_data;
> AVIOContext *pb = s->pb;
> @@ -1596,8 +1603,13 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
> end_ebml_master(pb, blockgroup);
> }
>
> - if ((codec->codec_type == AVMEDIA_TYPE_VIDEO && keyframe) || codec->codec_type == AVMEDIA_TYPE_SUBTITLE) {
> - ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, ts, mkv->cluster_pos, relative_packet_pos,
> + if ((codec->codec_type == AVMEDIA_TYPE_VIDEO && keyframe) ||
> + codec->codec_type == AVMEDIA_TYPE_SUBTITLE ||
> + add_cue) {
> + ret = mkv_add_cuepoint(mkv->cues,
> + pkt->stream_index,
> + mkv->is_dash ? mkv->dash_track_number : pkt->stream_index + 1,
> + ts, mkv->cluster_pos, relative_packet_pos,
> codec->codec_type == AVMEDIA_TYPE_SUBTITLE ? duration : -1);
> if (ret < 0) return ret;
> }
> @@ -1615,6 +1627,7 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
> int64_t cluster_time;
> AVIOContext *pb;
> int ret;
> + int start_new_cluster;
>
> if (mkv->tracks[pkt->stream_index].write_dts)
> cluster_time = pkt->dts - mkv->cluster_pts;
> @@ -1632,11 +1645,26 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
> cluster_size = avio_tell(pb);
> }
>
> - if (mkv->cluster_pos != -1 &&
> - (cluster_size > mkv->cluster_size_limit ||
> - cluster_time > mkv->cluster_time_limit ||
> - (codec_type == AVMEDIA_TYPE_VIDEO && keyframe &&
> - cluster_size > 4 * 1024))) {
> + if (mkv->is_dash && codec_type == AVMEDIA_TYPE_VIDEO) {
> + // WebM DASH specification states that the first block of every cluster
> + // has to be a key frame. So for DASH video, we only create a cluster
> + // on seeing key frames.
> + start_new_cluster = keyframe;
is it intended to have 1 frame per cluster for intra only videos ?
also, is there an easy way by which this patch can be tested ?
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
You can kill me, but you cannot change the truth.
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