[vlc-devel] 5.1 to stereo plugin with lookahead

[Mikel Astiz]

Hi Rémi,

Thanks for your clear answer. We will probably have to reconsider our initial approach, given the circumstances.

In any case, it will be necessary for us to synchronize the video and the audio, using "Audio desynchronization compensation". You say it can be done, but we haven't managed so far. In a filter, in headphone.c for example, if you change p_aout->pp_inputs[x]->i_desync, the change does not affect the system. Could you please elaborate on this approach?

I would also like to raise another basic question. Is it possible to know (or change) the frequency in which DoWork is called? I mean, our tests show that every call to DoWork is given about 1500 samples, at 30 Hz. Is this a fixed rate? Does it depend on the source being played?

Thanks,
Mikel


-----Mensaje original-----
De: vlc-devel-bounces at videolan.org [mailto:vlc-devel-bounces at videolan.org] En nombre de Rémi Denis
Enviado el: viernes, 24 de octubre de 2008 18:46
Para: Mailing list for VLC media player developers
Asunto: Re: [vlc-devel] 5.1 to stereo plugin with lookahead

   Hello,

> our algorithm needs to have not only the current sound signal (and the past),
> but also some seconds in
the future.

Fundamentally, VLC is a real-time player, owing to its origin as a stream receiver.
There are many audio postprocessing algorithms which depend on "future" samples, in our modern world. But several seconds is a really abnormally long delay. This is probably only acceptable in very specific scenarii.

> COULD SOMEONE CONFIRM THAT YOU CANNOT OBTAIN THE SAMPLES
> BEYOND THE CURRENT POSITION OF THE VIDEO?

 You can to SOME extent. Audio is always processed slightly ahead of time, as per include/vlc_config.h   
Not several seconds by default.

> The only solution we have found so far is to use the parameter
> "Audio desynchronization compensation".
> can you change this parameter programmatically in a plugin,
> without involving the user?

It would be ugly, but yes you can. 

 

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