Select provider of libav* libraries

[Jonas Smedegaard]

Quoting Alessandro Ghedini (2015-05-17 21:58:15)
> 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.

Oh.  Do I understand you correctly that neither wiki page nor README.md 
file is really relevant, but you have relevant personal experiences? If 
so, thanks for clarifying.  I agree that personal experience is relevant 
for this discussion.


>> Ok, so exotic subtitle formats is a "particular" reason for mpv authors 
>> to favor FFmpeg over libav.
>
> Where did you get the "exotic" part?

Sorry that I didn't clarify.  I wanted to avoid the misconception (among 
those reading along but not themselves using mpv) that _all_ mpv 
subtitle handling was broken with Libav (it certainly is not), and 
assumed from my own experience that those missing were less common than 
the ones supported in both of the libraries.  Please do correct me if 
that's wrong.


>> 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.

...and you do build against ffmpeg.  Targeted experimental.  No doubt 
those wanting it would prefer it being easier accessible than that, but 
if their reason was "just to be sure to have the most bleeding edge 
possible" then they'd never use our too boring stable release anyway.

We don't know their reasons, so can only speculate and that speculation 
can go in any direction, not only towards "ffmpeg is the better choice 
for Debian."


> It might be true that there is no major issue that makes libav 
> unusable for everyone,

I never said that.

My main concern is long-term maintainability.  Mpv was brought up as an 
upstream documenting why they favor ffmpeg and I tried isolate the parts 
in their documentation which might apply to us and weed out parts that 
might be irrelevant to us for long term maintenance.

Finding out if that concrete feature emphasized by mpv authors - better 
coverage of subtitle formats - was popular or not among us seemed to me 
to be a relevant question to raise.

But I do not try to make it sound like subtitle coverage is all that 
counts for us.  Or any other single feature.

I use bleeding edge tools for some of my own work.  And I use FFmpeg for 
some of that.  But I will continue to use bleeding edge tools for that 
work - which renders it irrelevant for judging what is relevant for long 
term maintenance in Debian.

Similarly I try to distinguish if reasons of others fit a constraint of 
long term maintenance or not.


> 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.

"supposed to be"? - are you somehow implying that you know the needs of 
our users and I do not (or do and don't give a shit)?


 - Jonas

-- 
 * Jonas Smedegaard - idealist & Internet-arkitekt
 * Tlf.: +45 40843136  Website: http://dr.jones.dk/

 [x] quote me freely  [ ] ask before reusing  [ ] keep private
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