Select provider of libav* libraries

[Alessandro Ghedini]

On Sun, May 17, 2015 at 08:43:57PM +0200, Jonas Smedegaard wrote:
> Quoting Alessandro Ghedini (2015-05-17 18:55:14)
> > On Sun, May 17, 2015 at 11:28:47AM +0200, Jonas Smedegaard wrote:
> >> Also, it is apparently not their current position
> >
> > From the README.md file [0]:
> >
> >> Generally, mpv should work with the latest release as well as the git 
> >> version of both FFmpeg and Libav. But FFmpeg is preferred, and some 
> >> mpv features work with FFmpeg only (subtitle formats in particular).
> >
> > So no, the position hasn't really changed, but I don't know why the 
> > wiki page was removed.
> 
> Ah, thanks for that hint: Git commit be6cca78 indicates that the wiki 
> edit was deliberate, and that their position indeed have changed: It has 
> shrunk from a wide range of issues to only concretely mention subtitles.

The issues mentioned in the page were hardly wide ranging. One was about the
fact that libav doesn't implement some video filters, which forces mpv to carry
its own implementations (still true). Another about about libav HTTP support
(most likely fixed but I'm not sure). The other were all about subtitles.

It's also true that the list wasn't really esaustive before it was deleted. For
example one time I tried to convert a part of a movie into a GIF with mpv,
before realizing that libav's GIF encoder is completely broken (I actually
tried to backport it from ffmpeg, before giving up and switching to ffmpeg
myself), but this wasn't mentioned in the wiki.

> Ok, so exotic subtitle formats is a "particular" reason for mpv authors 
> to favor FFmpeg over libav.

Where did you get the "exotic" part?

> I personally use mpv almost daily, with material from many different 
> sources.  I am not a native english speaker so appreciate material with 
> subtitles and sometimes fetch it myself, and would notice material 
> including subtitles but failing to work.  Nevertheless I do not recall 
> subtitles ever failing to work.  No doubt subtitles exist in weird 
> formats somewhere, but my point is that personally I have not needed any 
> of those more exotic subtitle formats.
> 
> How many of you can honestly say that you suffer from inferior subtitle 
> support in mpv in Debian (i.e. the package linked against libav)?

I've run into libav's lack of external vobsub files support several times
already. I've also seen broken PGS subtitles decoding in the wild, even though
I'm not really an avid watcher of BluRays.

Several people also expressly asked me to provide mpv packages built against
ffmpeg. I suppose they had their own reasons.

It might be true that there is no major issue that makes libav unusable for
everyone, but there are a lot of somewhat minor issues that make libav unusable
for many different use-cases (e.g. see Fabian's earlier email). Which is kinda
sad IMO, considering that the needs of our users is supposed to be one of
Debian's main priorities.

Cheers
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