[FFmpeg-cvslog] movenc: Add an option for enabling negative CTS offsets
Martin Storsjö
git at videolan.org
Tue Oct 31 02:07:04 EET 2017
ffmpeg | branch: master | Martin Storsjö <martin at martin.st> | Thu Apr 7 15:45:37 2016 +0300| [c380a0d7f7a2c7411aae60463e25d916541f0388] | committer: Martin Storsjö
movenc: Add an option for enabling negative CTS offsets
This reduces the need for an edit list; streams that start with
e.g. dts=-1, pts=0 can be encoded as dts=0, pts=0 (which is valid
in mov/mp4) by shifting the dts values of all packets forward.
This avoids the need for edit lists for such streams (while they
still are needed for audio streams with encoder delay).
This eases conformance with the DASH-IF interoperability guidelines.
Signed-off-by: Martin Storsjö <martin at martin.st>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c380a0d7f7a2c7411aae60463e25d916541f0388
---
libavformat/movenc.c | 28 ++++++++++++++++++++++++----
libavformat/movenc.h | 2 ++
2 files changed, 26 insertions(+), 4 deletions(-)
diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 840190dbfa..356d1d6b71 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -62,6 +62,7 @@ static const AVOption options[] = {
{ "delay_moov", "Delay writing the initial moov until the first fragment is cut, or until the first fragment flush", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_DELAY_MOOV}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
{ "global_sidx", "Write a global sidx index at the start of the file", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_GLOBAL_SIDX}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
{ "skip_trailer", "Skip writing the mfra/tfra/mfro trailer for fragmented files", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_SKIP_TRAILER}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
+ { "negative_cts_offsets", "Use negative CTS offsets (reducing the need for edit lists)", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_NEGATIVE_CTS_OFFSETS}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
FF_RTP_FLAG_OPTS(MOVMuxContext, rtp_flags),
{ "skip_iods", "Skip writing iods atom.", offsetof(MOVMuxContext, iods_skip), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM},
{ "iods_audio_profile", "iods audio profile atom.", offsetof(MOVMuxContext, iods_audio_profile), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 255, AV_OPT_FLAG_ENCODING_PARAM},
@@ -1163,8 +1164,9 @@ static int mov_write_stsd_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *tra
return update_size(pb, pos);
}
-static int mov_write_ctts_tag(AVIOContext *pb, MOVTrack *track)
+static int mov_write_ctts_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *track)
{
+ MOVMuxContext *mov = s->priv_data;
MOVStts *ctts_entries;
uint32_t entries = 0;
uint32_t atom_size;
@@ -1188,7 +1190,11 @@ static int mov_write_ctts_tag(AVIOContext *pb, MOVTrack *track)
atom_size = 16 + (entries * 8);
avio_wb32(pb, atom_size); /* size */
ffio_wfourcc(pb, "ctts");
- avio_wb32(pb, 0); /* version & flags */
+ if (mov->flags & FF_MOV_FLAG_NEGATIVE_CTS_OFFSETS)
+ avio_w8(pb, 1); /* version */
+ else
+ avio_w8(pb, 0); /* version */
+ avio_wb24(pb, 0); /* flags */
avio_wb32(pb, entries); /* entry count */
for (i = 0; i < entries; i++) {
avio_wb32(pb, ctts_entries[i].count);
@@ -1273,7 +1279,7 @@ static int mov_write_stbl_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *tra
mov_write_stss_tag(pb, track, MOV_PARTIAL_SYNC_SAMPLE);
if (track->par->codec_type == AVMEDIA_TYPE_VIDEO &&
track->flags & MOV_TRACK_CTTS && track->entry)
- mov_write_ctts_tag(pb, track);
+ mov_write_ctts_tag(s, pb, track);
mov_write_stsc_tag(pb, track);
mov_write_stsz_tag(pb, track);
mov_write_stco_tag(pb, track);
@@ -2594,7 +2600,10 @@ static int mov_write_trun_tag(AVIOContext *pb, MOVMuxContext *mov,
avio_wb32(pb, 0); /* size placeholder */
ffio_wfourcc(pb, "trun");
- avio_w8(pb, 0); /* version */
+ if (mov->flags & FF_MOV_FLAG_NEGATIVE_CTS_OFFSETS)
+ avio_w8(pb, 1); /* version */
+ else
+ avio_w8(pb, 0); /* version */
avio_wb24(pb, flags);
avio_wb32(pb, end - first); /* sample count */
@@ -3040,6 +3049,8 @@ static int mov_write_ftyp_tag(AVIOContext *pb, AVFormatContext *s)
ffio_wfourcc(pb, "MSNV");
else if (mov->mode == MODE_MP4 && mov->flags & FF_MOV_FLAG_DEFAULT_BASE_MOOF)
ffio_wfourcc(pb, "iso5"); // Required when using default-base-is-moof
+ else if (mov->mode == MODE_MP4 && mov->flags & FF_MOV_FLAG_NEGATIVE_CTS_OFFSETS)
+ ffio_wfourcc(pb, "iso4");
else if (mov->mode == MODE_MP4)
ffio_wfourcc(pb, "isom");
else if (mov->mode == MODE_IPOD)
@@ -3288,6 +3299,8 @@ static int mov_flush_fragment(AVFormatContext *s, int force)
if (!track->end_reliable) {
AVPacket pkt;
if (!ff_interleaved_peek(s, i, &pkt, 1)) {
+ if (track->dts_shift != AV_NOPTS_VALUE)
+ pkt.dts += track->dts_shift;
track->track_duration = pkt.dts - track->start_dts;
if (pkt.pts != AV_NOPTS_VALUE)
track->end_pts = pkt.pts;
@@ -3729,6 +3742,12 @@ static int mov_write_packet(AVFormatContext *s, AVPacket *pkt)
mov->flags &= ~FF_MOV_FLAG_FRAG_DISCONT;
}
+ if (mov->flags & FF_MOV_FLAG_NEGATIVE_CTS_OFFSETS) {
+ if (trk->dts_shift == AV_NOPTS_VALUE)
+ trk->dts_shift = pkt->pts - pkt->dts;
+ pkt->dts += trk->dts_shift;
+ }
+
if (!pkt->size) {
if (trk->start_dts == AV_NOPTS_VALUE && trk->frag_discont) {
trk->start_dts = pkt->dts;
@@ -4095,6 +4114,7 @@ static int mov_write_header(AVFormatContext *s)
track->start_dts = AV_NOPTS_VALUE;
track->start_cts = AV_NOPTS_VALUE;
track->end_pts = AV_NOPTS_VALUE;
+ track->dts_shift = AV_NOPTS_VALUE;
if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
if (track->tag == MKTAG('m','x','3','p') || track->tag == MKTAG('m','x','3','n') ||
track->tag == MKTAG('m','x','4','p') || track->tag == MKTAG('m','x','4','n') ||
diff --git a/libavformat/movenc.h b/libavformat/movenc.h
index f4ed188c38..008f4671c6 100644
--- a/libavformat/movenc.h
+++ b/libavformat/movenc.h
@@ -107,6 +107,7 @@ typedef struct MOVTrack {
int64_t start_cts;
int64_t end_pts;
int end_reliable;
+ int64_t dts_shift;
int hint_track; ///< the track that hints this track, -1 if no hint track is set
int src_track; ///< the track that this hint track describes
@@ -195,6 +196,7 @@ typedef struct MOVMuxContext {
#define FF_MOV_FLAG_DELAY_MOOV (1 << 13)
#define FF_MOV_FLAG_GLOBAL_SIDX (1 << 14)
#define FF_MOV_FLAG_SKIP_TRAILER (1 << 15)
+#define FF_MOV_FLAG_NEGATIVE_CTS_OFFSETS (1 << 16)
int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt);
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