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

[Måns Rullgård]

Robert Swain <robert.swain at gmail.com> writes:

> 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>:
>>>> 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?
>>
>> That depends on the target container.  E.g. MPEG doesn't need all the
>> timestamps.
>
> If MPEG doesn't need all the time stamps then would it spit that error
> in this situation?

The error is triggered whatever format is used.

-- 
M?ns Rullg?rd
mans at mansr.com