[alsa-devel] ALSA synchronization

Maxim Levitsky maximlevitsky at gmail.com
Sat Aug 22 14:12:10 CEST 2009

On Sat, 2009-08-22 at 18:50 +0700, arif setiawan wrote:
> Hi,
> We are working on audio processing (encryption-decryption) and audio will be
> sent using radio.
> Our configuration is :
> Audio source - ALSA audio in - encryption - ALSA audio out - transmission
> over radio (now we still use audio cable) - ALSA audio in - decryption -
> ALSA audio out - speaker.
> So data will be sent through radio channel and its converted to analog form
> by ALSA PCM during playback. We want to solve synchronization issue by using
> data header so that we can decrypt correct data block. So far we still
> unable to verify that data we received in the decryption side is similar to
> data that we sent from encryption box. Supposed that we filled buffer in
> encryption box with some values, when we check buffer in decryption box, we
> can't get same data. Our guess that data somehow changed in
> digital-analog/analog-digital conversion or we might make mistakes in
> filling the buffer so data is not compatible with ALSA PCM.
> Any suggestion to solve this problem?

Are you trying to say that you broadcast a digital data  over an analog
channel, and expect it to be unchanged, without any form of encoding,
error correction, etc...?

This is crazy!

Best regards,
	Maxim Levitsky

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