i.MX Processors中的主题 Re: Problem on sound speed

Problem on sound speed

victorien — Wed, 17 Jun 2015 12:21:07 GMT

Hi,

I make some audio test on my board : imx280, sgtl5000, Linux3.14, rootfs by OpenEmbedded and I play MP3 file with mpg123.

the issue is : my platform need 60s and 35ms to play a sound of 60s (it's take 60s on my computer). I try with another MP3 player and I have the same problem.

Is there someone who knows were is generate this changement of speed ?

Re: Problem on sound speed

CarlosCasillas — Mon, 22 Jun 2015 19:33:24 GMT

Hi,

Have you considered file open/close times on the embedded system? What about clock precision on the i.MX28 board?

In the other hand, I’m afraid that such Linux version and MP3 players are not supported by Freescale on the i.MX28 platform.

Hope this will be useful for you.
Best regards!
/Carlos

Re: Problem on sound speed

victorien — Tue, 23 Jun 2015 07:36:03 GMT

Hi,

Thanks for your answer. I made more tests and I found the reason of my problem : the issue is the SAIF clock. There are a bug on divider computing and the precision of the divider is not enough to provide a stable audio rate for a long time (cf chapter 35.2.1 of datasheet). I'm working on a correction.

Re: Problem on sound speed

jörg_krause — Mon, 29 Jun 2015 18:49:28 GMT

Hi,

do you like tho share your investigations? Many thanks!

Re: Problem on sound speed

victorien — Thu, 02 Jul 2015 07:39:00 GMT

Hi,

Sure, I can share !

I made 2 modifications :

- On mxs clock driver, I change the function which compute the divider to have the best result (cf patch 0001)

- The iMX28 datasheet says that the precision of divider in not enough to respect an audio/video synchronisation (chapter 35.2.1 page 2203). Then I had a process to change periodicaly the SAIF frequency (cf patch 0003)

This code is based on kernel 3.14 and I'm not sure that it is conformed to the "linux rule" then you can propose improvment !

Re: Problem on sound speed

jörg_krause — Thu, 02 Jul 2015 14:58:05 GMT

Many thanks for this! Great work!

I applied the patches without any problems on a 4.0 Kernel. The synchronisation is much better now. However sometimes the frequency is adjusted to a new value where after this a lot of sync errors occur. The frequency is adjusted to the old value after around 52 seconds and the sync is alright again. Do you know why the frequency is adjusted?

Re: Problem on sound speed

jörg_krause — Thu, 02 Jul 2015 15:16:21 GMT

I have got it! Every 420.1 seconds the frequency is adjusted for 52 seconds to maintain audio synchronization within +/-20ms, right?

Re: Problem on sound speed

victorien — Thu, 02 Jul 2015 15:25:49 GMT

Yes it's right. This part is explain on datasheet.

But I don't understand what do you mean by "However sometimes the frequency is adjusted to a new value where after this a lot of sync errors occur.".

This modification of the driver is under development, then I'm really interested by your comments and results

Re: Problem on sound speed

fabio_estevam — Thu, 02 Jul 2015 15:38:56 GMT

Good job, Victorien!

Does it take exactly 60s for the track to play with your changes applied?

When you are happy with the fix, please let me know and I can help you submitting your changes to the mainline kernel.

Regards,

Fabio Estevam

Re: Problem on sound speed

jörg_krause — Thu, 02 Jul 2015 17:15:59 GMT

victorien Let me explain: The source DACs clock (a remote music player) has coincidentally the same "wrong" clock frequency which is not adjusted. The first 420 seconds both are running "synchronous". After 52 seconds my clock is running faster then the remotes clock and the device has to do some corrections to maintain synchronization with the slower remote clock.

So, as you see, this is not a problem of your patch. So forget about this - it just took me a while to understand what's happening here :-)

Re: Problem on sound speed

jörg_krause — Mon, 06 Jul 2015 19:53:39 GMT

As the patch 1 is a bugfix we should really submit it to mainline kernel!

Re: Problem on sound speed

fabio_estevam — Mon, 06 Jul 2015 19:59:48 GMT

I agree, Jörg. If you or Victorien could send it, that would be awesome. Please note that the patch misses a Signed-off-by tag.

Re: Problem on sound speed

victorien — Tue, 07 Jul 2015 07:00:09 GMT

I'm agree and I'll submit it to mainline. Do you have any comment about this patch ? improvment ? respect of kernel rule ?

And it will be the first time I submit a patch to list ; what is the best way to do ?

Re: Problem on sound speed

lategoodbye — Tue, 07 Jul 2015 12:07:06 GMT

Hi Victorien,

your patch is a candidate for a stable fix, so your changes should be short as possible. It would be helpful to describe in short how to reproduce the problem.

Please look at Linux/Documentation/SubmittingPatches - Linux Cross Reference - Free Electrons for more details.

Re: Problem on sound speed

fabio_estevam — Tue, 07 Jul 2015 14:00:21 GMT

Hi Victorien,

Patches look good. Need some minor adjustments.

1. Run ./scripts/checkpatch.pl on both of them and fix the reported issues.

For example: Signed-off-by line is missing, no "//" style comments, use /* Test 123 */ style instead,

code should be placed under 80 columns, etc.

After all these issues are handled, then improve a bit the commit log and provide some examples on how the rate is currently set and what is the new rate after the patch is applied, how the problem can be reproduced.

Then send it to the list using git send-email and Cc the maintainers and lists involved. Running ./scripts/get_maintainers will tell you who to Cc on your patch.

If you have questions about this process, just ask us.

Regards,

Fabio Estevam

Re: Problem on sound speed

lategoodbye — Fri, 31 Jul 2015 06:45:33 GMT

Hi Victorien,

do you still want to submit this patch to mainline? In the case you don't have the time please let us know.

Regards

Stefan Wahren

Re: Problem on sound speed

victorien — Fri, 31 Jul 2015 16:28:03 GMT

Hi,

I was really busy in July and I forgot to do that. I submitted the patch today. I hope it will be accept !!!

Re: Problem on sound speed

fabio_estevam — Sun, 02 Aug 2015 14:56:30 GMT

Hi Victorien,

I was not able to find your patch in the alsa-devel list. Have you subscribed to this list?

Regards,

Fabio Estevam

Re: Problem on sound speed

lategoodbye — Sun, 02 Aug 2015 16:41:45 GMT

Hi Fabio,

Victorien send it to linux-kernel which is correct:

'[PATCH] clk:mxs: Fix bug on frequency divider' - MARC

Regards Stefan

Re: Problem on sound speed

fabio_estevam — Sun, 02 Aug 2015 17:01:34 GMT

Hi Stefan,

get_maintainer.pl suggests the following folks and lists:

$ ./scripts/get_maintainer.pl -f drivers/clk/mxs/clk-frac.c

Michael Turquette <mturquette@baylibre.com> (maintainer:COMMON CLK FRAMEWORK)

Stephen Boyd <sboyd@codeaurora.org> (maintainer:COMMON CLK FRAMEWORK,commit_signer:1/1=100%,authored:1/1=100%,removed_lines:1/1=100%)

Shawn Guo <shawn.guo@linaro.org> (commit_signer:1/1=100%)

linux-clk@vger.kernel.org (open list:COMMON CLK FRAMEWORK)

linux-kernel@vger.kernel.org (open list)

Regards,

Fabio Estevam