[Ffmpeg-devel] PTS / DTS with XViD

[Jani Boutellier]

Rich Felker wrote:
> On Tue, Jul 18, 2006 at 10:32:40AM +0100, M?ns Rullg?rd wrote:
>
>> Rich Felker said:
>>
>>> On Tue, Jul 18, 2006 at 08:39:04AM +0100, M?ns Rullg?rd wrote:
>>>
>>>>>> OGM doesn't know anything about B-frames (it has all the same
>>>>>> limitations as AVI in that regard). And all containers I've ever
>>>>>> heard of store frames in decoding order.
>>>>>> --Loren Merritt
>>>>>>
>>>>>
>>>>> Are you sure?
>>>>>
>>>>> Both of these sites indicate that there should be B-frame support:
>>>>> http://www.divxland.org/container_formats.php
>>>>> http://en.wikipedia.org/wiki/Comparison_of_container_formats
>>>>
>>>>
>>>> Both are wrong, as is to be expected of sites like those.  Which do
>>>> you trust, random websites or people who actually read specs and write
>>>> code?
>>>
>>>
>>> I have plenty of OGM files with B frames.
>>
>>
>> Perhaps, but that doesn't mean the format supports it.
>
>
>
> The OGM format is not sanctioned by Xiph and was designed by windows
> kiddies to store "DirectShow content" in OGG. Thus it should probably
> be interpreted just like AVI..
>
>
>>> If OGM only has one
>>> timestamp then it almost surely needs to be interpreted as dts, not
>>> pts... :(
>>
>>
>> Yes, probably.
>
>
>
> Yet another broken format... :(
>
> Rich


As a concluding remark, I'll have to state that the problem was not at all 
in the OGM format.
After hours of trial and error I managed to get the XViD-encoded video into 
a MPEG4 -container (.mp4). Surprisingly the the abovementioned problem with 
OGM occurred also with mp4, so I figured that the true source of problems 
was XViD.
Soon I discovered that the video clips I had used, contained a so-called 
"packed bitstream", which meant that the B-frames were crammed inside 
P-frames. After I changed this in encoding settings and re-encoded the 
video clips, the decoding worked well.
This means that although the OGM format was labeled as a "broken format" in 
this thread, it probably would work well also with b-frames. However, I 
didn't try that in practice anymore, since I'm happy with mp4 now :)

-- 
Jani Boutellier