[linux-dvb] Re: V4 API proposal

[Andreas Oberritter <andreas@oberritter.de>]

On Mon, 2003-03-10 at 15:00, Marcus Metzler wrote:
> Johannes Stezenbach writes:
> 
>  > Currently the API makes no guarantee on data alignment when you read()
>  > PES data from the demux. For sections, it is guaranteed that each read()
>  > wil get exactly one section with the start of the section at the start
>  > of the buffer, provided the buffer is large enough. If the buffer is too
>  > small, consecutive read()s will get the remainder of the section.
>  > 
>  > We could try to do the same for PES filters, or shouldn't we?
>  > 
> 
> There are various problems with that.
> 
> 1) You don't know how long a video PES will be when it starts.
> 2) There is no maximum size for video PES.
> 3) The TS is usually not muxed on the PES level, at least from my
>    experience.
> 
> This will lead to much larger problems than finding a PES header.

Yes, finding the end of a video pes packet is horrible. :)

However, most demux hardware should provide the option to wait for the
pusi flag in the ts header before delivering data. It would be nice if
one could select this pusi-wait-flag from userspace, so that the first
read() after setting the demux filter starts with a pes header if
desired. Or maybe this should even be default for every new pes filter? 

Regards,
Andreas



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