Bad playback speed while playing WAV and MP3 file

Technical Support
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1

Hi,

I have an image built for Colibri T20 with Yocto Poky Morty and necessary tegra layers.
I have also gstreamer 1.0 with all necessary plugins.
I’m now experiencing weird playback issues with an example WAV file (rec in 44100) and MP3 file.
As I try to launch it with gstreamer, the playback sound a little bit slower than expected.
I thought that maybe my gstreamer config was screwed.

So I tried to play the WAV file with alsa tool aplay.
And it sounds the same, that is a little bit slower.

Therefore I was wondering if I had to change settings in some config file.
I didn’t find much resources for the Colibri T20 and it sound processor.
Could it be related to the rate of the file and the rate of the device ?

Thanks for your feedback.

Karim

PS: I have performed the same test with a fresh LXDE image and aplay: same result.

2

Yes, I believe natively AC97 may only play 48 kHz audio. Other sample rates would need explicit conversion.

3

Thanks for your feedback Marcel.

Do you mean that there is no way at all to play files in 44KHZ ?
What about changing the ALSA settings in

/usr/share/alsa/alsa.conf

or

/etc/.asoundrc

Not being a specialist, It seems to be doable.

However, in the current Linux image, changing these settings have no effect.

Do you know if there are some settings specific for Colibri T20 boards ?
Is it the same thing for mp3 or m4a file contents ?

Thanks.

Karim

4

Thanks for your feedback Marcel.

You are very welcome.

Do you mean that there is no way at all to play files in 44KHZ ?

No, not at all. Other sample rates would just need explicit conversion e.g. using audioresample.

What about changing the ALSA settings in
/usr/share/alsa/alsa.conf
or
/etc/.asoundrc

I don’t think any such settings change anything in that regard.

Not being a specialist, It seems to be doable.

However, in the current Linux image, changing these settings have no effect.

Do you know if there are some settings specific for Colibri T20 boards ?

No, I don’t think so.

Is it the same thing for mp3 or m4a file contents ?

Yes, I guess so.

5

Hi Marcel,

You’re right. Using the audioresample plugin can fix this issue.
I have tested it successfully in command line.

The problem is, I’m using Qt5.7 and the QMultimedia framework and I don’ know how it’s possible to force the use of this plugin…as this layer is abstracted by Qt.

Have you already experienced this kind of issue ?

Best Regards,

Karim

6

We do not have Qt expertise. However, for wav playback the QAudioOutput class might me more appropriate. One can pass a QAudioFormat object which allows setting the sample rate while initialising the QAudioOutput class object.