[FFmpeg-devel] Supporting container formats with PTS gaps (Ogg)

Robert Swain robert.swain
Mon Feb 2 15:39:39 CET 2009

2009/2/2 M?ns Rullg?rd <mans at mansr.com>:
> Robert Swain <robert.swain at gmail.com> writes:
>> 2009/2/2 M?ns Rullg?rd <mans at mansr.com>:
>>> Peter Ross <pross at xvid.org> writes:
>>>> This is adequate for simple playback, but when copying an Ogg file
>>>> to another format, things break. For example, the ffmpeg program
>>>> tries to calculate the DTS value from the previous PTS (see
>>>> output_packet() ffmpeg.c ~1396). There is some other functional
>>>> cruft in libavformat that attempts to calculate PTS from DTS
>>>> (compute_pkt_fields2() in libavformat/utils.c ~2548).
>>> I consider this mess a flaw in the FFmpeg design.  Some formats
>>> provide only occasional timestamps, and there is no generic way to
>>> find the missing timestamps without (more or less) decoding the
>>> elementary streams.  The current approach seems to be vigorous denial
>>> of this, and a half-baked attempt at inventing the missing
>>> timestamps.  More often than not this fails, resulting in the infamous
>>> "non-monotone timestamps" error when stream-copying.
>> This issue seems to come up quite a lot. What can be done to make the
>> system more robust? Is decoding the elementary streams the only way?
>> If so, shouldn't this 'brute force' approach at the very least be an
>> option?
> Timestamp interpolation should only be done when required, not by
> default.

That's why I said at the very least be an option, rather than just
spitting the "non-monotone timestamps" error. In this situation would
it not be considered required?


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