[FFmpeg-devel] [PATCH] libavformat/matroskaenc: Add WebM DASH support
Vignesh Venkatasubramanian
vigneshv at google.com
Wed May 7 18:46:40 CEST 2014
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;
+ } else if (mkv->is_dash && codec_type == AVMEDIA_TYPE_AUDIO &&
+ cluster_time > mkv->cluster_time_limit) {
+ // For DASH audio, we create a Cluster based on cluster_time_limit
+ start_new_cluster = 1;
+ } else if (!mkv->is_dash &&
+ (cluster_size > mkv->cluster_size_limit ||
+ cluster_time > mkv->cluster_time_limit ||
+ (codec_type == AVMEDIA_TYPE_VIDEO && keyframe &&
+ cluster_size > 4 * 1024))) {
+ start_new_cluster = 1;
+ } else {
+ start_new_cluster = 0;
+ }
+
+ if (mkv->cluster_pos != -1 && start_new_cluster) {
av_log(s, AV_LOG_DEBUG, "Starting new cluster at offset %" PRIu64
" bytes, pts %" PRIu64 "dts %" PRIu64 "\n",
avio_tell(pb), pkt->pts, pkt->dts);
@@ -1649,7 +1677,9 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
// check if we have an audio packet cached
if (mkv->cur_audio_pkt.size > 0) {
- ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt);
+ // for DASH audio, a CuePoint has to be added when there is a new cluster.
+ ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt,
+ mkv->is_dash ? start_new_cluster : 0);
av_free_packet(&mkv->cur_audio_pkt);
if (ret < 0) {
av_log(s, AV_LOG_ERROR, "Could not write cached audio packet ret:%d\n", ret);
@@ -1670,7 +1700,7 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
ret = av_copy_packet_side_data(&mkv->cur_audio_pkt, &mkv->cur_audio_pkt);
}
} else
- ret = mkv_write_packet_internal(s, pkt);
+ ret = mkv_write_packet_internal(s, pkt, 0);
return ret;
}
@@ -1706,7 +1736,7 @@ static int mkv_write_trailer(AVFormatContext *s)
// check if we have an audio packet cached
if (mkv->cur_audio_pkt.size > 0) {
- ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt);
+ ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt, 0);
av_free_packet(&mkv->cur_audio_pkt);
if (ret < 0) {
av_log(s, AV_LOG_ERROR, "Could not write cached audio packet ret:%d\n", ret);
@@ -1821,6 +1851,8 @@ static const AVOption options[] = {
{ "reserve_index_space", "Reserve a given amount of space (in bytes) at the beginning of the file for the index (cues).", OFFSET(reserve_cues_space), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, FLAGS },
{ "cluster_size_limit", "Store at most the provided amount of bytes in a cluster. ", OFFSET(cluster_size_limit), AV_OPT_TYPE_INT , { .i64 = -1 }, -1, INT_MAX, FLAGS },
{ "cluster_time_limit", "Store at most the provided number of milliseconds in a cluster.", OFFSET(cluster_time_limit), AV_OPT_TYPE_INT64, { .i64 = -1 }, -1, INT64_MAX, FLAGS },
+ { "dash", "Create a WebM file conforming to WebM DASH specification", OFFSET(is_dash), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, FLAGS },
+ { "dash_track_number", "Track number for the DASH stream", OFFSET(dash_track_number), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 127, FLAGS },
{ NULL },
};
--
1.9.1.423.g4596e3a
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