> - // Offset the DTS by ctts[0] to make the PTS of the first frame 0
> - if (ctts_data_old && ctts_count_old > 0) {
> - edit_list_dts_entry_end -= ctts_data_old[0].duration;
> - av_log(mov->fc, AV_LOG_DEBUG, "Offset DTS by ctts[%d].duration:
%d\n", 0, ctts_data_old[0].duration);
> + av_log(mov->fc, AV_LOG_DEBUG, "Shifting DTS by %d because of
negative CTTS.\n", msc->dts_shift);
> }
The above lines were the cause of making the first frame PTS of videos
starting with B-frames negative. If the videos starts with B frame, then
the minimum composition time as computed by stts + ctts will be non-zero.
Hence we need to shift the DTS, so that the first pts is zero. This was the
intention of that code-block. However it was subtracting by the wrong
amount.
For example, for one of the videos in the bug nonFormatted.mp4 we have
stts:
sample_count duration
960 1001
ctts:
sample_count duration
1 3003
2 0
1 3003
....
The resulting composition times are : 3003, 1001, 2002, 6006, ...
Hence the minimum composition time or PTS is 1001, which should be used to
offset DTS. However the code block was wrongly using ctts[0] which is 3003
. Hence the PTS was negative.
About the fate test expectations, fate-suite/h264/twofields_packet.mp4 is a
similar file starting with 2 Bframes. Before this change the PTS of first
two B-frames was -6006 and -3003, and I am guessing one of them got dropped
when being decoded and remuxed to the framecrc before, and now it is not
being dropped but I dont understand why.
On Sat, Jun 3, 2017 at 5:40 AM, wm4 <nfx...@googlemail.com> wrote:
> On Fri, 2 Jun 2017 18:17:22 -0700
> Sasi Inguva <isasi-at-google....@ffmpeg.org> wrote:
>
> > Fixes t/6421
> >
> > Signed-off-by: Sasi Inguva <is...@google.com>
> > ---
> > libavformat/mov.c | 57 ++++++++++++++++++++++++------
> ----
> > tests/ref/fate/h264-twofields-packet | 60
> ++++++++++++++++++------------------
> > 2 files changed, 70 insertions(+), 47 deletions(-)
> >
> > diff --git a/libavformat/mov.c b/libavformat/mov.c
> > index 3845e63b53..d7d64c3361 100644
> > --- a/libavformat/mov.c
> > +++ b/libavformat/mov.c
> > @@ -3039,6 +3039,9 @@ static void mov_fix_index(MOVContext *mov,
> AVStream *st)
> > int64_t edit_list_dts_entry_end = 0;
> > int64_t edit_list_start_ctts_sample = 0;
> > int64_t curr_cts;
> > + int64_t curr_ctts = 0;
> > + int64_t min_corrected_pts = -1;
> > + int64_t empty_edits_sum_duration = 0;
> > int64_t edit_list_index = 0;
> > int64_t index;
> > int64_t index_ctts_count;
> > @@ -3053,6 +3056,7 @@ static void mov_fix_index(MOVContext *mov,
> AVStream *st)
> > int first_non_zero_audio_edit = -1;
> > int packet_skip_samples = 0;
> > MOVIndexRange *current_index_range;
> > + int i;
> >
> > if (!msc->elst_data || msc->elst_count <= 0 || nb_old <= 0) {
> > return;
> > @@ -3080,13 +3084,9 @@ static void mov_fix_index(MOVContext *mov,
> AVStream *st)
> >
> > // If the dts_shift is positive (in case of negative ctts values in
> mov),
> > // then negate the DTS by dts_shift
> > - if (msc->dts_shift > 0)
> > + if (msc->dts_shift > 0) {
> > edit_list_dts_entry_end -= msc->dts_shift;
> > -
> > - // Offset the DTS by ctts[0] to make the PTS of the first frame 0
> > - if (ctts_data_old && ctts_count_old > 0) {
> > - edit_list_dts_entry_end -= ctts_data_old[0].duration;
> > - av_log(mov->fc, AV_LOG_DEBUG, "Offset DTS by ctts[%d].duration:
> %d\n", 0, ctts_data_old[0].duration);
> > + av_log(mov->fc, AV_LOG_DEBUG, "Shifting DTS by %d because of
> negative CTTS.\n", msc->dts_shift);
> > }
> >
> > start_dts = edit_list_dts_entry_end;
> > @@ -3100,6 +3100,7 @@ static void mov_fix_index(MOVContext *mov,
> AVStream *st)
> > edit_list_dts_entry_end += edit_list_duration;
> > num_discarded_begin = 0;
> > if (edit_list_media_time == -1) {
> > + empty_edits_sum_duration += edit_list_duration;
> > continue;
> > }
> >
> > @@ -3179,11 +3180,13 @@ static void mov_fix_index(MOVContext *mov,
> AVStream *st)
> >
> > // frames (pts) before or after edit list
> > curr_cts = current->timestamp + msc->dts_shift;
> > + curr_ctts = 0;
> >
> > if (ctts_data_old && ctts_index_old < ctts_count_old) {
> > - av_log(mov->fc, AV_LOG_DEBUG, "shifted frame pts,
> curr_cts: %"PRId64" @ %"PRId64", ctts: %d, ctts_count: %"PRId64"\n",
> > - curr_cts, ctts_index_old,
> ctts_data_old[ctts_index_old].duration, ctts_count_old);
> > - curr_cts += ctts_data_old[ctts_index_old].duration;
> > + curr_ctts = ctts_data_old[ctts_index_old].duration;
> > + av_log(mov->fc, AV_LOG_DEBUG, "stts: %"PRId64" ctts:
> %"PRId64", ctts_index: %"PRId64", ctts_count: %"PRId64"\n",
> > + curr_cts, curr_ctts, ctts_index_old,
> ctts_count_old);
> > + curr_cts += curr_ctts;
> > ctts_sample_old++;
> > if (ctts_sample_old == ctts_data_old[ctts_index_old].count)
> {
> > if (add_ctts_entry(&msc->ctts_data,
> &msc->ctts_count,
> > @@ -3244,14 +3247,21 @@ static void mov_fix_index(MOVContext *mov,
> AVStream *st)
> > }
> > }
> > }
> > - } else if (edit_list_start_encountered == 0) {
> > - edit_list_start_encountered = 1;
> > - // Make timestamps strictly monotonically increasing
> for audio, by rewriting timestamps for
> > - // discarded packets.
> > - if (st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO &&
> frame_duration_buffer) {
> > - fix_index_entry_timestamps(st,
> st->nb_index_entries, edit_list_dts_counter,
> > - frame_duration_buffer,
> num_discarded_begin);
> > - av_freep(&frame_duration_buffer);
> > + } else {
> > + if (min_corrected_pts < 0) {
> > + min_corrected_pts = edit_list_dts_counter +
> curr_ctts + msc->dts_shift;
> > + } else {
> > + min_corrected_pts = FFMIN(min_corrected_pts,
> edit_list_dts_counter + curr_ctts + msc->dts_shift);
> > + }
> > + if (edit_list_start_encountered == 0) {
> > + edit_list_start_encountered = 1;
> > + // Make timestamps strictly monotonically
> increasing for audio, by rewriting timestamps for
> > + // discarded packets.
> > + if (st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO
> && frame_duration_buffer) {
> > + fix_index_entry_timestamps(st,
> st->nb_index_entries, edit_list_dts_counter,
> > +
> frame_duration_buffer, num_discarded_begin);
> > + av_freep(&frame_duration_buffer);
> > + }
> > }
> > }
> >
> > @@ -3292,6 +3302,19 @@ static void mov_fix_index(MOVContext *mov,
> AVStream *st)
> > }
> > }
> > }
> > + // If there are empty edits, then min_corrected_pts might be
> positive intentionally. So we subtract the
> > + // sum duration of emtpy edits here.
> > + min_corrected_pts -= empty_edits_sum_duration;
> > +
> > + // If the minimum pts turns out to be greater than zero after
> fixing the index, then we subtract the
> > + // dts by that amount to make the first pts zero.
> > + if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO &&
> min_corrected_pts > 0) {
> > + av_log(mov->fc, AV_LOG_DEBUG, "Offset DTS by %"PRId64" to make
> first pts zero.\n", min_corrected_pts);
> > + for (i = 0; i < st->nb_index_entries; ++i) {
> > + st->index_entries[i].timestamp -= min_corrected_pts;
> > + }
> > + }
> > +
> > // Update av stream length
> > st->duration = edit_list_dts_entry_end - start_dts;
> >
> > diff --git a/tests/ref/fate/h264-twofields-packet b/tests/ref/fate/h264-
> twofields-packet
> > index 4cff0a15bd..db12498f15 100644
> > --- a/tests/ref/fate/h264-twofields-packet
> > +++ b/tests/ref/fate/h264-twofields-packet
> > @@ -3,33 +3,33 @@
> > #codec_id 0: rawvideo
> > #dimensions 0: 1920x1080
> > #sar 0: 1/1
> > -0, 0, 0, 1, 3110400, 0x40d65f69
> > -0, 1, 1, 1, 3110400, 0xdcbc50bf
> > -0, 2, 2, 1, 3110400, 0x73a2276a
> > -0, 3, 3, 1, 3110400, 0x84a2b3c6
> > -0, 4, 4, 1, 3110400, 0x7cf3b570
> > -0, 5, 5, 1, 3110400, 0xa2d1e03a
> > -0, 6, 6, 1, 3110400, 0x03220fb1
> > -0, 7, 7, 1, 3110400, 0x89cd526a
> > -0, 8, 8, 1, 3110400, 0xbb4b7531
> > -0, 9, 9, 1, 3110400, 0x0a69f053
> > -0, 10, 10, 1, 3110400, 0x0187994b
> > -0, 11, 11, 1, 3110400, 0x26ed49fa
> > -0, 12, 12, 1, 3110400, 0xbe8966d4
> > -0, 13, 13, 1, 3110400, 0x248d203c
> > -0, 14, 14, 1, 3110400, 0x3139c754
> > -0, 15, 15, 1, 3110400, 0xf22380c4
> > -0, 16, 16, 1, 3110400, 0x3e00dcc1
> > -0, 17, 17, 1, 3110400, 0x8cbe2483
> > -0, 18, 18, 1, 3110400, 0x6951cd63
> > -0, 19, 19, 1, 3110400, 0x36aca4c5
> > -0, 20, 20, 1, 3110400, 0x4d4f6fbe
> > -0, 21, 21, 1, 3110400, 0x997247aa
> > -0, 22, 22, 1, 3110400, 0x0fd40e06
> > -0, 23, 23, 1, 3110400, 0xa10d2d67
> > -0, 24, 24, 1, 3110400, 0x87c481da
> > -0, 25, 25, 1, 3110400, 0xe3dca3cd
> > -0, 26, 26, 1, 3110400, 0x5f77b078
> > -0, 27, 27, 1, 3110400, 0xf1ddd098
> > -0, 28, 28, 1, 3110400, 0xedcd1754
> > -0, 29, 29, 1, 3110400, 0x14ac7153
> > +0, 0, 0, 1, 3110400, 0x48e39acd
> > +0, 1, 1, 1, 3110400, 0x40d65f69
> > +0, 2, 2, 1, 3110400, 0xdcbc50bf
> > +0, 3, 3, 1, 3110400, 0x73a2276a
> > +0, 4, 4, 1, 3110400, 0x84a2b3c6
> > +0, 5, 5, 1, 3110400, 0x7cf3b570
> > +0, 6, 6, 1, 3110400, 0xa2d1e03a
> > +0, 7, 7, 1, 3110400, 0x03220fb1
> > +0, 8, 8, 1, 3110400, 0x89cd526a
> > +0, 9, 9, 1, 3110400, 0xbb4b7531
> > +0, 10, 10, 1, 3110400, 0x0a69f053
> > +0, 11, 11, 1, 3110400, 0x0187994b
> > +0, 12, 12, 1, 3110400, 0x26ed49fa
> > +0, 13, 13, 1, 3110400, 0xbe8966d4
> > +0, 14, 14, 1, 3110400, 0x248d203c
> > +0, 15, 15, 1, 3110400, 0x3139c754
> > +0, 16, 16, 1, 3110400, 0xf22380c4
> > +0, 17, 17, 1, 3110400, 0x3e00dcc1
> > +0, 18, 18, 1, 3110400, 0x8cbe2483
> > +0, 19, 19, 1, 3110400, 0x6951cd63
> > +0, 20, 20, 1, 3110400, 0x36aca4c5
> > +0, 21, 21, 1, 3110400, 0x4d4f6fbe
> > +0, 22, 22, 1, 3110400, 0x997247aa
> > +0, 23, 23, 1, 3110400, 0x0fd40e06
> > +0, 24, 24, 1, 3110400, 0xa10d2d67
> > +0, 25, 25, 1, 3110400, 0x87c481da
> > +0, 26, 26, 1, 3110400, 0xe3dca3cd
> > +0, 27, 27, 1, 3110400, 0x5f77b078
> > +0, 28, 28, 1, 3110400, 0xf1ddd098
> > +0, 29, 29, 1, 3110400, 0xedcd1754
>
> Thanks for the fix, but is there any explanation why this happens? And
> why does the FATE test change?
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>
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