How to have correct sound surround 5.1 over hdmi on iMX6 ?

[francoisrey]

I try to output a video with an 5.1 audio track encoded with AAC.

For this I use an Apalis IMX6Q with an Ixora carrier board, and the linux-3.14.28 supplied by Toradex.

I use gstreamer 0.10 with this command :

gst-launch filesrc location=/media/sda1/FILE2_AAC_5-1_TestVideo.mp4 typefind=true ! aiurdemux name=demux demux. ! queue ! vpudec low-latency=true ! imxv4l2sink demux. ! queue ! beepdec ! alsasink device=plughw:2,0

But the track of the Surround Right goes on the Front Center, the track of the Front Center goes on the Surrond Left and the track of the Surround Left goes nowhere.

For this test I use the following video : https://www2.iis.fraunhofer.de/AAC/multichannel.html

If I play the video with my computer on Ubuntu 14.04 its work well.

Anybody have a solution to get the correct output ?

[igorpadykov]

you are right, correct is chapter 15. However nxp documentation

does not mention this in other places or provide steps for testing, so

seems driver is not fully integrated in multimedia framework.

Note, if third party bsp is used it is responsibility of software vendor

to provide necessary functionality.

~igor

[igorpadykov]

Hi francoisrey

seems playing sound surround 5.1 sound will require dolby codecs,

these are licensed codecs and may be obtained through local marketing

contacts.

Best regards

igor

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[francoisrey]

Hi Igor,

thanks for your answer.

I think the AC3 codec requires a Dolby license, but not the AAC codec.

[igorpadykov]

Hi francoisrey

one can look at 7.1 codec (cs42888) description in attached Linux Manual

sect.28.2 SoC Sound Card and Linux Guide sect.7.3.1 Playback use cases

Best regards

igor

[francoisrey]

It seems that the cs42888 codec converts the digital signals to analog signals up to 8 channels. I do not see why I should use it to send the audio signal through the HDMI which has digital signals.

[igorpadykov]

I am afraid nxp bsp supports only 2 audio channels as described

in Linux Manual sect.16.1 Introduction :

"HDMI audio playback (2 channels, 16/24 bit, 44.1 KHz sample rate)"

If you are using toradex sw one can ask support for that feature from them.

Best regards

igor

[francoisrey]

In fact I use the "On-Chip High Definition Multimedia Interface" (chapter 15) not the "External High Definition Multimedia Interface" (chapter 16).

The "On-Chip HDMI" it is not only for demo application and it supports HDMI audio playback (2, 4, 6, or 8 channels, 16 bit, for sample rates 32KHz to 192 KHz).

But as I said in my first question, 3 channels are correct, 2 channels goes on bad speaker and one channel does not go out.