Re: [FFmpeg-devel] [PATCH 1/2] movenc: Add an option for enabling negative CTS offsets

[Michael Niedermayer]

On Sat, Sep 23, 2017 at 06:44:44PM +0300, Jan Ekström wrote:
> From: Martin Storsjö 
> 
> 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 
> ---
>  libavformat/movenc.c | 28 
>  libavformat/movenc.h |  2 ++
>  2 files changed, 26 insertions(+), 4 deletions(-)

This is missing a update to the docs

[...]
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[FFmpeg-devel] [PATCH 1/2] movenc: Add an option for enabling negative CTS offsets

[Jan Ekström]

From: Martin Storsjö 

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 
---
 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 10b959ad02..917486384a 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -77,6 +77,7 @@ static const AVOption options[] = {
 { "write_gama", "Write deprecated gama atom", 0, AV_OPT_TYPE_CONST, {.i64 
= FF_MOV_FLAG_WRITE_GAMA}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, 
"movflags" },
 { "use_metadata_tags", "Use mdta atom for metadata.", 0, 
AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_USE_MDTA}, 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_BOOL, {.i64 = 1}, 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},
@@ -2094,8 +2095,9 @@ static int mov_write_stsd_tag(AVFormatContext *s, 
AVIOContext *pb, MOVMuxContext
 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;
@@ -2119,7 +2121,11 @@ 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);
@@ -2303,7 +2309,7 @@ static int mov_write_stbl_tag(AVFormatContext *s, 
AVIOContext *pb, MOVMuxContext
 if (track->par->codec_type == AVMEDIA_TYPE_VIDEO &&
 track->flags & MOV_TRACK_CTTS && track->entry) {
 
-if ((ret = mov_write_ctts_tag(pb, track)) < 0)
+if ((ret = mov_write_ctts_tag(s, pb, track)) < 0)
 return ret;
 }
 mov_write_stsc_tag(pb, track);
@@ -4044,7 +4050,10 @@ 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 */
@@ -4489,6 +4498,8 @@ 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)
@@ -4759,6 +4770,8 @@ static int mov_flush_fragment(AVFormatContext *s, int 
force)
 if (!track->end_reliable) {
 AVPacket pkt;
 if (!ff_interleaved_peek(s, i, , 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;
@@ -5282,6 +5295,12 @@ static int mov_write_single_packet(AVFormatContext *s, 
AVPacket *pkt)
 mov->flags &= ~FF_MOV_FLAG_FRAG_DISCONT;
 }
 
+if (mov->flags & FF_MOV_FLAG_NEGATIVE_CTS_OFFSETS) {
+if