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movenc: Add some comments explaining subtle details in writing the edit lists

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Signed-off-by: Martin Storsjö <martin@martin.st>
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Martin Storsjö 2014-10-11 23:56:24 +03:00
parent 72f801619a
commit 95ee4e2ce7
1 changed files with 8 additions and 0 deletions
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8
libavformat/movenc.c
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@ -1620,6 +1620,11 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVTrack *track)
avio_wb32(pb, entry_count); avio_wb32(pb, entry_count);
if (delay > 0) { /* add an empty edit to delay presentation */ if (delay > 0) { /* add an empty edit to delay presentation */
/* In the positive delay case, the delay includes the cts
* offset, and the second edit list entry below trims out
* the same amount from the actual content. This makes sure
* that the offsetted last sample is included in the edit
* list duration as well. */
if (version == 1) { if (version == 1) {
avio_wb64(pb, delay); avio_wb64(pb, delay);
avio_wb64(pb, -1); avio_wb64(pb, -1);
@ -1634,6 +1639,9 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVTrack *track)
* here, but use FFMIN in case dts is a a small positive integer * here, but use FFMIN in case dts is a a small positive integer
* rounded to 0 when represented in MOV_TIMESCALE units. */ * rounded to 0 when represented in MOV_TIMESCALE units. */
start_ct = -FFMIN(track->cluster[0].dts, 0); start_ct = -FFMIN(track->cluster[0].dts, 0);
/* Note, this delay is calculated from the pts of the first sample,
* ensuring that we don't reduce the duration for cases with
* dts<0 pts=0. */
duration += delay; duration += delay;
} }