Re: Decoding stream

Hi Reno,

the xvid encoder can e.g. encode a raw YV12 stream as input and produces a
raw MPEG-4 Visual stream as output. For each input frame the encoder
provides you with one coded frame as output that can be of variable size.

The raw MPEG-4 output is preceded by MPEG-4 header information like VOL, VOP
headers just as defined in the MPEG-4 standard (see ISO/IEC 14496-2).

The xvid decoder works basically the same, just inverse. You feed the decoder
with a full frame of raw MPEG-4 coded data (can be of variable size) and the
decoder will provide you with e.g. a YV12 picture as output.

Most of the time, real applications don't store or transmit the xvid encoder
output as a raw stream. Rather, the xvid encoder output is usually muxed into
a container format (like AVI or MP4) that also stores the frame size along
with the raw coded data in the container and permits interleaved storage of
audio and video streams. Then upon decoding it's easy to determine the size
of a coded frame and ensure that the decoder is provided with sufficient
data.

Actually however, the above is real basic information and not at all specific
to xvid. Container formats and muxing/demuxing requirements generally apply
to all codecs and the 'one frame in -> one frame out' paradigm is quite
common too. You should really do some basic research first. A lot of info on
these topics can be found on the internet.

Regards,
Michael


Quoting reno reballos <[email protected]>:

> Hi Michael,
>
> i have read about the discussions in here with respect to decoding a  
>  raw mpeg-4 stream compressed by the xvid encoder too and i think  
> and  i hope i am in a right track to ask this question which is also  
>  related to encoding and decoding of stream using xvid source code  
> too.
>
> correct me if i am wrong, the xvid encoder (i.e. xvid_encraw)   
> encodes raw frames and the product of the encoder is the raw mpeg4   
> stream? does this raw mpeg4 bit stream contains any headers of the   
> vxid?
>
>
> thank you..
> looking forward to hear from you
>
>
> regards,
> reno
>
>
>
>
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