[Mp4-tech] [video]Padding in non standard videos

[Herbert Thoma]

Hi,
I believe that the file is correct.
The encoder can put what it likes into the not displayed
rows (140 - 143). The decoder has to use these decoded
pixel values in case of UMV.
See subclause 7.6.4 of ISO/IEC 14496-2:2004:
"Note that for rectangular VOP, a reference VOP is defined by
video_object_layer_width and video_object_layer_height, extended
to a multiple of 16."
We had a discussion about this padding issue on this reflector
at the end of November 2006.
Kind regards,
 Herbert.
Gururaj Bhat schrieb:
> Hi all,
> 
> I have attached a file of size 176 x 140 (pigs.3gp) which when played on my
> decoder,is showing pink patches at the bottom.
> I feel that this is a non standard file in which the encoder has not padded
> the remaining 4 columns with the last pel data ( ie with column 140) but
> with some random data which in this case happens to be pink.
> I guess that when the decoder has UMV ( unlimited motion vector's) which
> point outside the frame size 176 x 140 it picks up this random data and
> that's the reason for the pink patches to be seen.
> Some other decoders also play this file similarly but decoders like
> quicktime , real player etc play the file without any pink patches.
> Could you please check how this file plays with your decoders ?
> I would be interested in knowing how the MPEG VM ( verification models)
> play
> out this file .
> 
> You can refer to subclause 7.6.1 of the MPEG-4 standard which explains
> about
> the padding process for non-standard sizes.
> 
> Thanks
> 
> 
> 
> On 2/15/07, pankaj bajpai <pankaj_bajpai_iet operamail.com> wrote:
>>
>> Dear Gururaj,
>>
>> In the sequence header, it is the original size ie non-padded size
>> that need to be put.
>>
>> with regards
>>
>> > ----- Original Message -----
>> > From: "Gururaj Bhat" <bs.guru gmail.com>
>> > To: "pankaj bajpai" <pankaj_bajpai_iet operamail.com>
>> > Subject: Re: [Mp4-tech] [video]Padding in non standard videos
>> > Date: Wed, 14 Feb 2024 11:21:39 +0530
>> >
>> >
>> > Hi Pankaj,
>> >
>> > Thanks for your answer.
>> > I have one more doubt.Suppose it is padded,then what is the frame size
>> that
>> > has to be incorporated in the header of the encoded file?is it the
>> original
>> > size or the padded size?
>> >
>> > Suppose the padded size is included,then is there any way for the
>> decoder to
>> > know that the video is padded,and how much?
>> >
>> > Thanks in advance.
>> >
>> >
>> >
>> >
>> > On 2/14/07, pankaj bajpai <pankaj_bajpai_iet operamail.com> wrote:
>> > >
>> > > Dear Gururaj ,
>> > >
>> > > Yes encoder need to take care of padding. This is because the DCT is
>> > > performed on the 8x8 blocks. SO for border MBs, if you dont do
>> padding,
>> > > there will not be sufficient elements to perform DCT.
>> > >
>> > > With regards
>> > >
>> > >
>> > > > From: Gururaj Bhat <bs.guru gmail.com>
>> > > > To: mp4-tech lists.mpegif.org
>> > > > Subject: [Mp4-tech] [video]Padding in non standard videos
>> > > > Date: Tue, 13 Feb 2024 16:17:03 +0530
>> > > >
>> > > >
>> > > > Hi all,
>> > > >
>> > > > I have a case in which the encoded mpeg4 video is of size 176*140.
>> > > > Since the macroblock size is 16*16,140/16 is not an integer.
>> > > > So,does encoder need to take care to pad the video frame while
>> encoding?
>> > > > or is it the duty of the decoder?
>> > > >
>> > > > regards,
>> > > > Gururaj Bhat
>> > > >
>> > >
>> > >
>> > >
>> > > Pankaj Kumar Bajpai
>> > > Mulitimedia Engineer
>> > > India
>> > >
>> > >
>> > > --
>> > > _______________________________________________
>> > > Search for products and services at:
>> > > http://search.mail.com
>> > >
>> > > Powered by Outblaze
>> > >
>>
>> >
>>
>>
>>
>> Pankaj Kumar Bajpai
>> Mulitimedia Engineer
>> India
>>
>>
>> -- 
>> _______________________________________________
>> Search for products and services at:
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>>
>> Powered by Outblaze
>>
> 
> 
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-- 
Herbert Thoma
Head of Video Group
Multimedia Realtime Systems Department
Fraunhofer IIS
Am Wolfsmantel 33, 91058 Erlangen, Germany
Phone: +49-9131-776-323
Fax:   +49-9131-776-399
email: tma iis.fhg.de
www: http://www.iis.fhg.de/