Re: Xvid-devel Digest, Vol 90, Issue 1

If I remember correctly, xvid and Virtualdub participate in an ugly hack 
which lets vdub work around delayed frames problem. As long as xvid 
fills its bframe buffers it responds with a single-byte frames of some 
particular byte (0x80?). Virtualdub, or any other VfW application aware 
of this fact, will not put those frames to avi but will instead count them.
When stream ends, virtualdub feeds the very last frame more than once, 
based on this count, to extract delayed frames and obtain the right 
number of encoded frames.

You can do the same, which will work around VfW's limitation. Ideally 
though you shouldn't use avi with xvid (at least with b-frames) because, 
as you can see, it just doesn't work.

Regards


On 16/08/2010 5:34 AM, Yong Zhao wrote:
> Thanks to Peter. Can you give me a detailed description on how to disable
> the b-frames encoding. I tried but came up with nothing. Also, the problem
> only happens when I use Xvid as compression method in my own program. In the
> program I use the cvCreateVideoWriter and cvWriteFrame function
> from openCV to deal with generating and writing frame into AVI. When I used
> Xvid to compress some videos in VirtualDub, then the problem did not occur.
> In both cases, I use the same default parameters in Xvid configuration
> panel. The problem seems really weired.
>
> I hope someone can help.
>
>
> Yong
>
> On Sun, Aug 15, 2010 at 6:00 AM,<[email protected]>  wrote:
>
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>> Today's Topics:
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>>    1. an apparent bug (Yong Zhao)
>>    2. Re: an apparent bug (Peter Ross)
>>
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>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sat, 14 Aug 2010 20:39:21 -0400
>> From: Yong Zhao<[email protected]>
>> Subject: [XviD-devel] an apparent bug
>> To: [email protected]
>> Message-ID:
>>         <[email protected]>
>> Content-Type: text/plain; charset=ISO-8859-1
>>
>> Hi all,
>>
>> I use Xvid as my first choice compression method, and rarely come into
>> finding the problem I found today. Whenever you compress video materials
>> using Xvid, I find Xvid could result in the first 2 or 3 frame to be same
>> as
>> the first frame, and then come to the next sequential frames? Did everyone
>> else find the same problem? If so, has this bug been reported?
>>
>>
>> Yong
>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Sun, 15 Aug 2010 11:41:05 +1000
>> From: Peter Ross<[email protected]>
>> Subject: Re: [XviD-devel] an apparent bug
>> To: [email protected]
>> Message-ID:<[email protected]>
>> Content-Type: text/plain; charset=us-ascii; x-action=pgp-signed
>>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> On Sat, Aug 14, 2010 at 08:39:21PM -0400, Yong Zhao wrote:
>>> Hi all,
>>>
>>> I use Xvid as my first choice compression method, and rarely come into
>>> finding the problem I found today. Whenever you compress video materials
>>> using Xvid, I find Xvid could result in the first 2 or 3 frame to be same
>> as
>>> the first frame, and then come to the next sequential frames? Did
>> everyone
>>> else find the same problem? If so, has this bug been reported?
>>
>> No. I suspect you are encoding to AVI with b-frames enabled, and are
>> witnessing the b-frames decoder-presentation delay. If so, this is normal.
>>
>> - -- Peter
>> (A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
>> -----BEGIN PGP SIGNATURE-----
>> Version: GnuPG v1.4.10 (GNU/Linux)
>>
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>> Kz4AniZfgRqPmVjjUvtI+TtDA3UYGvyF
>> =Woo0
>> -----END PGP SIGNATURE-----
>>
>>
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>> End of Xvid-devel Digest, Vol 90, Issue 1
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