[FFmpeg-devel] [PATCH] avformat/nut: fix duration estimation by writting EOR packets
Michael Niedermayer
michael at niedermayer.cc
Mon Dec 17 20:52:57 EET 2018
On Mon, Dec 17, 2018 at 07:32:49PM +0100, Paul B Mahol wrote:
> On 12/17/18, Michael Niedermayer <michael at niedermayer.cc> wrote:
> > On Mon, Dec 17, 2018 at 06:04:40PM +0100, Paul B Mahol wrote:
> >> Hi,
> >>
> >> patches attached.
> >
> >> nut.h | 2 +
> >> nutdec.c | 3 ++
> >> nutenc.c | 87
> >> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
> >> 3 files changed, 88 insertions(+), 4 deletions(-)
> >> 870df19d733f29294a2cb2e3ea5ed1a09745f3a4
> >> 0001-avformat-nut-fix-duration-estimation-by-writing-EOR-.patch
> >> From 80d6805fdf386182341fe72035ab88e06a602752 Mon Sep 17 00:00:00 2001
> >> From: Paul B Mahol <onemda at gmail.com>
> >> Date: Mon, 17 Dec 2018 16:43:57 +0100
> >> Subject: [PATCH 1/2] avformat/nut: fix duration estimation by writing EOR
> >> packets
> >>
> >> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> >> ---
> >> libavformat/nut.h | 2 +
> >> libavformat/nutdec.c | 3 ++
> >> libavformat/nutenc.c | 87 ++++++++++++++++++++++++++++++++++++++++++--
> >> 3 files changed, 88 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/libavformat/nut.h b/libavformat/nut.h
> >> index a4409ee23d..d7ba86b5e5 100644
> >> --- a/libavformat/nut.h
> >> +++ b/libavformat/nut.h
> >> @@ -76,6 +76,8 @@ typedef struct StreamContext {
> >> int last_flags;
> >> int skip_until_key_frame;
> >> int64_t last_pts;
> >> + int64_t last_dts;
> >> + int64_t last_duration;
> >> int time_base_id;
> >> AVRational *time_base;
> >> int msb_pts_shift;
> >> diff --git a/libavformat/nutdec.c b/libavformat/nutdec.c
> >> index 056ef59d00..f2490f9842 100644
> >
> >> --- a/libavformat/nutdec.c
> >> +++ b/libavformat/nutdec.c
> >> @@ -1080,6 +1080,9 @@ static int decode_frame(NUTContext *nut, AVPacket
> >> *pkt, int frame_code)
> >>
> >> stc = &nut->stream[stream_id];
> >>
> >> + if (stc->last_flags & FLAG_EOR)
> >> + return 1;
> >
> > EOR can occur in the middle of subtitle streams. It would be used to mark
> > areas with no vissible subtitles.
> > (The point behind this is that it allows seeking to consider a subtitle
> > stream
> > if and only if there are actually any displayed subtitles at that time)
> >
> > this code would break that
> >
> > also demxuer and muxer changes should be in seperate patches
> >
> >
> >> +
> >> if (stc->last_flags & FLAG_KEY)
> >> stc->skip_until_key_frame = 0;
> >>
> >> diff --git a/libavformat/nutenc.c b/libavformat/nutenc.c
> >> index e9a3bb49db..c12b4cc8cf 100644
> >> --- a/libavformat/nutenc.c
> >> +++ b/libavformat/nutenc.c
> >> @@ -940,6 +940,80 @@ fail:
> >> return ret;
> >> }
> >>
> >> +static void nut_update_max_pts(AVFormatContext *s, int stream_index,
> >> int64_t pts)
> >> +{
> >> + NUTContext *nut = s->priv_data;
> >> + StreamContext *nus = &nut->stream[stream_index];
> >> +
> >> + if (!nut->max_pts_tb || av_compare_ts(nut->max_pts, *nut->max_pts_tb,
> >> pts, *nus->time_base) < 0) {
> >> + nut->max_pts = pts;
> >> + nut->max_pts_tb = nus->time_base;
> >> + }
> >> +}
> >> +
> >> +static int nut_write_eor(AVFormatContext *s, int stream_index)
> >> +{
> >> + AVIOContext *bc = s->pb, *dyn_bc;
> >> + NUTContext *nut = s->priv_data;
> >> + StreamContext *nus = &nut->stream[stream_index];
> >> + int ret, frame_code, flags, needed_flags;
> >> + int64_t pts = nus->last_pts + nus->last_duration;
> >> + int64_t coded_pts;
> >> + FrameCode *fc;
> >> +
> >> + coded_pts = pts & ((1 << nus->msb_pts_shift) - 1);
> >> + if (ff_lsb2full(nus, coded_pts) != pts)
> >> + coded_pts = pts + (1 << nus->msb_pts_shift);
> >> +
> >> + nut->last_syncpoint_pos = avio_tell(bc);
> >> + ret = avio_open_dyn_buf(&dyn_bc);
> >> + if (ret < 0)
> >> + return ret;
> >> + put_tt(nut, nus->time_base, dyn_bc, nus->last_dts +
> >> nus->last_duration);
> >> + ff_put_v(dyn_bc, 0);
> >> +
> >> + if (nut->flags & NUT_BROADCAST) {
> >> + put_tt(nut, nus->time_base, dyn_bc,
> >> + av_rescale_q(av_gettime(), AV_TIME_BASE_Q,
> >> *nus->time_base));
> >> + }
> >> + put_packet(nut, bc, dyn_bc, 1, SYNCPOINT_STARTCODE);
> >> +
> >> + frame_code = -1;
> >> + for (int i = 0; i < 256; i++) {
> >> + FrameCode *fc = &nut->frame_code[i];
> >> + int flags = fc->flags;
> >> +
> >> + if (flags & FLAG_INVALID)
> >> + continue;
> >> +
> >> + if (!(flags & FLAG_CODED)) {
> >> + continue;
> >> + }
> >> +
> >> + frame_code = i;
> >> + break;
> >> + }
> >> + av_assert0(frame_code != -1);
> >> +
> >> + fc = &nut->frame_code[frame_code];
> >> + flags = fc->flags;
> >> + needed_flags = FLAG_KEY | FLAG_EOR | FLAG_CODED_PTS |
> >> FLAG_STREAM_ID;
> >> +
> >> + ffio_init_checksum(bc, ff_crc04C11DB7_update, 0);
> >> + avio_w8(bc, frame_code);
> >> + if (flags & FLAG_CODED) {
> >> + ff_put_v(bc, (flags ^ needed_flags) & ~(FLAG_CODED));
> >> + flags = needed_flags;
> >> + }
> >> + if (flags & FLAG_STREAM_ID) ff_put_v(bc, stream_index);
> >> + if (flags & FLAG_CODED_PTS) ff_put_v(bc, coded_pts);
> >> + ffio_get_checksum(bc);
> >> +
> >> + nut_update_max_pts(s, stream_index, nus->last_pts +
> >> nus->last_duration);
> >> +
> >> + return 0;
> >> +}
> >> +
> >> static int nut_write_packet(AVFormatContext *s, AVPacket *pkt)
> >> {
> >> NUTContext *nut = s->priv_data;
> >> @@ -1136,6 +1210,8 @@ static int nut_write_packet(AVFormatContext *s,
> >> AVPacket *pkt)
> >>
> >> nus->last_flags = flags;
> >> nus->last_pts = pkt->pts;
> >> + nus->last_dts = pkt->dts;
> >> + nus->last_duration = pkt->duration;
> >>
> >> //FIXME just store one per syncpoint
> >> if (flags & FLAG_KEY && !(nut->flags & NUT_PIPE)) {
> >> @@ -1150,10 +1226,7 @@ static int nut_write_packet(AVFormatContext *s,
> >> AVPacket *pkt)
> >> nus->keyframe_pts[nut->sp_count] = pkt->pts;
> >> }
> >>
> >> - if (!nut->max_pts_tb || av_compare_ts(nut->max_pts, *nut->max_pts_tb,
> >> pkt->pts, *nus->time_base) < 0) {
> >> - nut->max_pts = pkt->pts;
> >> - nut->max_pts_tb = nus->time_base;
> >> - }
> >> + nut_update_max_pts(s, pkt->stream_index, pkt->pts);
> >>
> >> fail:
> >> av_freep(&sm_buf);
> >> @@ -1167,6 +1240,12 @@ static int nut_write_trailer(AVFormatContext *s)
> >> AVIOContext *bc = s->pb, *dyn_bc;
> >> int ret;
> >>
> >> + for (int i = 0; i < s->nb_streams; i++) {
> >> + ret = nut_write_eor(s, i);
> >> + if (ret < 0)
> >> + return ret;
> >> + }
> >> +
> >> while (nut->header_count < 3)
> >> write_headers(s, bc);
> >
> > This violates the packet interleaving requirements
> > if one stream ends. lets say at time 5sec and one continues with frames at
> > 6,7,8 sec then the EOR frame for the stream ending at 5sec has to be
> > written
> > before the later frames.
>
> How this violates it? It writes it at end. After end there is nothing.
from nut.txt:
"pts of all frames in all streams MUST be bigger or equal to dts of all
previous frames in all streams, compared in common timebase. (EOR
frames are NOT exempt from this rule.)"
so if you have 2 streams (i assume for simplicity they have dts=pts)
with a pts=dts assumtation the above rule requires all frames to be
simply ordered by timestamp
A Time: 1 2 4 5
A len : 1 2 1 1
B Time: 1 2 3 5 6 7 8
B len : 1 1 2 1 1 1 1
Now the EOR frame for A would have timestamp 6 (5 + length(1)) and
the last frame for B has timestamp 8, the EOR for it would be 9
that means the EOR of A would have to be stored around the place where
the frame for B with timestamp 6 is. If its stored later then there
would be a frame in stream B stored with a timestamp larger than the
later EOR for A violating the rule
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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