[FFmpeg-devel] [PATCH v3 1/2] lavf/avienc: Add support for palette side data packets

[Mats Peterson]

On 02/28/2016 12:16 PM, Reimar Döffinger wrote:
>> And Reimar, the AVI muxer libavformat/avienc.c uses *lots* of avio_seek()
>> all over the place, so it won't work well on stdout regardless of my patch.
>> I have checked for avio_seek() returning >= 0 in my part of the code in any
>> case, but it won't make much of a difference.
>
> I think the effect of a failed avio_seek is kind of undefined, so
> checking the result is not really right as by then it's already broken.
>

Well, the documentation says that avio_seek() is a variant of the 
fseek() function. I would rather say it's a variant of lseek(), since it 
returns the new position, not just 0 or -1. In any case, this is what 
the lseek() man page says:

"On error, the value (off_t) -1 is returned and  errno  is  set  to 
indicate the error."

So it's not really undefined.

I also disagree with your analysis, all other avio_seek I could find
> are under if (pb->seekable), even if it is sometimes quite non-obvious.

Yes, I've noticed that.

> Also it might be helpful for you to have a look at tests/fate/demux.mak
> and tests/fate/video.mak and use copy-paste to write some basic tests
> for all the things you implement, so it doesn't get broken the moment
> you look the other way...

Yes, but I'm completely new at writing FATE tests, and it seems very 
complex to me, so I'll take a rain check on that one. Hopefully Michael 
will be able to add some good tests for the palette stuff, when he's got 
the time for it.

Mats