Re: [alsa-devel] ALSA synchronization
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?
Thank you,
Best Regards,
Arif
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
2009/8/22 arif setiawan n.arif.setiawan@gmail.com:
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?
Where is the conversion from digital to analogue on the output direction? Where is the modulation and error correction happening on the radio bit, in between the encrypt and decrypt steps. You should probably do a test without the encrypt and decrypt stages, and just ensure the input equals the output.
Kind regards
James
Hi,
Thank you for the input. I think we have been neglecting digital-analog conversion issue until now. We don't have any experiences in broadcast a digital data over an analog channel.
I think we should learn encoding, modulation and error correction now using google and others. That being said, I think this is not ALSA domain, however, any references and working example would be helpful for us.
Thank you,
Best Regards
Arif
On Sun, Aug 23, 2009 at 5:10 AM, James Courtier-Dutton < james.dutton@gmail.com> wrote:
2009/8/22 arif setiawan n.arif.setiawan@gmail.com:
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?
Where is the conversion from digital to analogue on the output direction? Where is the modulation and error correction happening on the radio bit, in between the encrypt and decrypt steps. You should probably do a test without the encrypt and decrypt stages, and just ensure the input equals the output.
Kind regards
James
participants (3)
-
arif setiawan -
James Courtier-Dutton -
Maxim Levitsky