[Bluez-devel] a2dpd and mplayer - any chance to get it working? [resent]

[Bluez-devel] a2dpd and mplayer - any chance to get it working? [resent]

[Robert Huitl]

Hi,

I was wondering whether it is possible to make the a2dp alsa plugin supply 
correct audio timing to applications like MPlayer. Right now, MPlayer does 
not work with a2dpd because it relies on the audio driver to report accurate 
audio timing information (or something like that).

If a2dpd could measure the delay introduced on the wireless transport, it 
might be possible to supply timing information to media players. The player 
could then sync the video to the audio data, so there should be no delay at 
all between audio and video playback.

Is there something I am missing?
What changes to the alsa plugin would be necessary?

Even if the delay can't be determined exactly, we could just fake that 
information MPlayer is missing, so that a2dpd at least worked together with 
MPlayer (with a small delay, maybe)?

Regards,
  Robert

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Re: [Bluez-devel] a2dpd and mplayer - any chance to get it working? [resent]

[Brad Midgley]

Robert

> I was wondering whether it is possible to make the a2dp alsa plugin supply 
> correct audio timing to applications like MPlayer. Right now, MPlayer does 
> not work with a2dpd because it relies on the audio driver to report accurate 
> audio timing information (or something like that).
> 
> If a2dpd could measure the delay introduced on the wireless transport, it 
> might be possible to supply timing information to media players. The player 
> could then sync the video to the audio data, so there should be no delay at 
> all between audio and video playback.
> 
> Is there something I am missing?
> What changes to the alsa plugin would be necessary?
> 
> Even if the delay can't be determined exactly, we could just fake that 
> information MPlayer is missing, so that a2dpd at least worked together with 
> MPlayer (with a small delay, maybe)?

we have a couple of things to address here.

For one, the delay can change over time. It might be 250ms on startup
but if I walk out of range and come back then all the transmission
problems have caused it to go up to 400ms.

Another is the delay likely varies from set to set.

We could start with a guess like 300ms and see how that covers it. If
lib alsa provides what we need, it's probably a snd_pcm_hw_params_set_*
function to be invoked in a2dpd_output_alsa.c.

Brad

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