From 95ee4e2ce774e0339632d067161596bf3dadfc72 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Martin=20Storsj=C3=B6?= Date: Sat, 11 Oct 2014 23:56:24 +0300 Subject: [PATCH] movenc: Add some comments explaining subtle details in writing the edit lists MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Martin Storsjö --- libavformat/movenc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/libavformat/movenc.c b/libavformat/movenc.c index 4017a56158..218aa5012a 100644 --- a/libavformat/movenc.c +++ b/libavformat/movenc.c @@ -1620,6 +1620,11 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVTrack *track) avio_wb32(pb, entry_count); 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) { avio_wb64(pb, delay); 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 * rounded to 0 when represented in MOV_TIMESCALE units. */ 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; } -- GitLab