FFmpeg

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Author	SHA1	Message	Date
Dale Curtis	37e8edc9f5	avformat/mov: Fix trampling of ctts during seeks when sidx support is enabled. When sidx box support is enabled, the code will skip reading all trun boxes (each containing ctts entries for samples inthat box). If seeks are attempted before all ctts values are known, the old code would dump ctts entries into the wrong location. These are then used to compute pts values which leads to out of order and incorrectly timestamped packets. This patch fixes ctts processing by always using the index returned by av_add_index_entry() as the ctts_data index. When the index gains new entries old values are reshuffled as appropriate. This approach makes sense since the mov demuxer is already relying on the mapping of AVIndex entries to samples for correct demuxing. As a result of this all ctts entries are now 1-count. A followup change will be submitted to remove support for > 1 count entries which will simplify seeking. Notes for future improvement: Probably there are other boxes (stts, stsc, etc) that are impacted by this issue... this patch only attempts to fix ctts since it completely breaks packet timestamping. This patch continues using an array for the ctts data, which is not the most ideal given the rearrangement that needs to happen (via memmove as new entries are read in). Ideally AVIndex and the ctts data would be set-type structures so addition is always worst case O(lg(n)) instead of the O(n^2) that exists now; this slowdown is noticeable during seeks. Signed-off-by: Dale Curtis <dalecurtis@chromium.org> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>	7 years ago

Author

SHA1

Message

Date

Dale Curtis

37e8edc9f5

avformat/mov: Fix trampling of ctts during seeks when sidx support is enabled.

When sidx box support is enabled, the code will skip reading all
trun boxes (each containing ctts entries for samples inthat box).

If seeks are attempted before all ctts values are known, the old
code would dump ctts entries into the wrong location. These are
then used to compute pts values which leads to out of order and
incorrectly timestamped packets.

This patch fixes ctts processing by always using the index returned
by av_add_index_entry() as the ctts_data index. When the index gains
new entries old values are reshuffled as appropriate.

This approach makes sense since the mov demuxer is already relying
on the mapping of AVIndex entries to samples for correct demuxing.

As a result of this all ctts entries are now 1-count. A followup
change will be submitted to remove support for > 1 count entries
which will simplify seeking.

Notes for future improvement:
Probably there are other boxes (stts, stsc, etc) that are impacted
by this issue... this patch only attempts to fix ctts since it
completely breaks packet timestamping.

This patch continues using an array for the ctts data, which is not
the most ideal given the rearrangement that needs to happen (via
memmove as new entries are read in). Ideally AVIndex and the ctts
data would be set-type structures so addition is always worst case
O(lg(n)) instead of the O(n^2) that exists now; this slowdown is
noticeable during seeks.

Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

7 years ago

1 Commits (220603d0c83ef1fe2727813f81bab5a96cfb046d)