[vlc-devel] 5.1 to stereo plugin with lookahead

[Kaarlo Räihä]

Mikel Astiz kirjoitti 24.10.2008 kello 13:04:
> Hello,
> 
>  
> 
> We are trying to develop a plugin for VLC, which mixes the 6 channels of
> a 5.1 source into a stereo output, just like
> "modules/audio_filter/channel_mixer/headphone.c" does.
> 
>  
> 
> However, there is an important issue: our algorithm needs to have not
> only the current sound signal (and the past), but also some seconds in
> the future. In other words, to be able to calculate the output of a
> certain time T, we need to have the data ranging from [T-K1 to T+K2],
> where K1 and K2 involve several seconds (about 5, for example).
> 
>  
> 
> (This behaviour is inherent in the algorithm and impossible to modify,
> so please do not focus on this issue)
> 
>  
> 
> We've been trying different approaches, using audio filters or audio
> mixers, but the function DoWork apparently is never given the sound
> signal of the "future". Could someone confirm this? COULD SOMEONE
> CONFIRM THAT YOU CANNOT OBTAIN THE SAMPLES BEYOND THE CURRENT POSITION
> OF THE VIDEO?
> 
>  
> 
> The only solution we have found so far is to use the parameter "Audio
> desynchronization compensation". This can delay the video output, and
> makes it possible to have all the audio input several seconds before the
> corresponding video is played. This approach raises another question:
> can you change this parameter (Audio desynchronization compensation)
> programmatically in a plugin, without involving the user?
> 

You can set the desync value from plugin, but IMHO I don't think that is "proper" way to this. 

>  
> 
> Any suggestions will be welcome.
> 
>  
> 
> Thanks in advance,
> 
> Mikel Astiz
> 
>  
> 
>  
> 


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