Panda: hdmi audio only on 2 channels

[Eckhard Diezel]

Installed the linarotv image 20120114-2 and hwpack_linaro-lt-panda-x11-base_20120106-1 on a Pandaboard ES with linaro-media-create.
After boot installed ubuntu-omap4-extras-multimedia.

HDMI connected to a Yamaha RX-V1800 audio-video-receiver and from there to a 1080p plasma.

Verified multichannel audio with xbmc.

xbmc settings:

Audio output: HDMI
Speaker Configuration: 5.1
Audio output device: Defaults (ALSA)
Passthrough output devive: hdmi (ALSA)

1. when passthrough is enabled AC3 sound in videos does not work

2. when passthrough is disabled only 2 audio channels are transmitted to the AVR (AVR display has indicators showing which channels are in use)

Crosschecked with alsa speaker-test (speaker-test -c6 -t wav) with same result:

Output correct for front left, front right and center (the latter only because the pro-logic decoder in the AVR puts sound equal to left and right onto the center) but rear sound is played with low volume on the front speakers.

Situation remains after update/dist-upgrade on Jan 21. 20:45CET.

Attaching the EDID sent by the AVR in case the audio capabilities are used by the driver (EDID is recorded with SwitchResX on a MacBook).

[Ricardo Salveti (rsalveti)]

Andy, do you know if this is something that's supported at Panda? And if so, if it was ever tested with your current kernel tree?

[warmcat (andy-warmcat)]

No, I only have 2-channel TV, we have never been asked to look at 5.1

[Tom Gall (tom-gall)]

Can twl even drive 5.1? From the docs, it feels like stereo output is as good as it gets.

[Jassi Brar (jassisinghbrar)]

Andy: OMAP HDMI cpu dai doesn't support anything other than Stereo.
   It seems rather hardcoded in hdmi_audio_hw_params.

Tom: I doubt if TWL has anything to do with HDMI audio, which shouldn't
   a real codec.

[warmcat (andy-warmcat)]

Thanks Jassi.... I'm going to set this to wishlist on our side then. I don't know if the hardware can do 5.1 but this starts to become an R&D effort rather than a bug. I realize it might be important for Ubuntu TV but if we will work on it we need some steer that TI would like us to do that (and that we're not wasting our time vs the hardware capability).

[Eckhard Diezel (ecdi)]

A snippet from an OMAP4430 Technical Reference Manual:

> 10.4.1.1 HDMI Main Features
...
> Uncompressed multi-channel (up to 8 channels) audio (L-PCM) support

No word about compressed digital audio passthrough. But as long as the decoders for those formats are part of the software 8 channel LPCM is enough for TV and video playback to 5.1/7.1 systems.

[Rob Clark (rob-ti)]

The hw supports multi-channel HDMI out (which isn't going thru TWL, fwiw).. but from what I can tell the upstream hdmi-audio driver does not yet. I think there are versions floating around in the past which have, but there is a lot of hdmi related cleanup still ongoing between dss hdmi, and asoc.

[warmcat (andy-warmcat)]

There are some nice patches from Ricardo Neri for this now, we will integrate and test them for omap4 in next weeks.

[Kurt Taylor (krtaylor)]

Driver issue that won't be fix in this code base - new driver coming via TI LT as per last comment.

[Ricardo Salveti (rsalveti)]

Andy, any update on your testing based on the comment #9?

[warmcat (andy-warmcat)]

Yeah they are integrated in the new OMAP45 tree at tracking-topic-hdmi-51a.

I confirmed yesterday that 2ch HDMI Audio is working there on a 4460.

I see there are instructions in the original post for 6ch test.

Next time my 4460 is bootable ^^ I'll try it out.

[warmcat (andy-warmcat)]

Trying it out involved buying a 5.1 amp.

The patchset we have supports 6 or 8 channels, but it seems there's a problem actually using 6 due to detail of buffer size

# speaker-test -Dhw:1,0 -c6

speaker-test 1.0.24.2

Playback device is hw:1,0
Stream parameters are 48000Hz, S16_LE, 6 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 64 to 10922
Period size range from 32 to 5440
Using max buffer size 10920
Unable to set buffer size 10920 for playback: Invalid argument
Setting of hwparams failed: Invalid argument

If I tell it to use 8 it likes the buffer size better and proceeds with the test.

# speaker-test -Dhw:1,0 -c8

speaker-test 1.0.24.2

Playback device is hw:1,0
Stream parameters are 48000Hz, S16_LE, 8 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 16 to 8192
Period size range from 8 to 4096
Using max buffer size 8192
Periods = 4
was set period_size = 2048
was set buffer_size = 8192
 0 - Front Left
 4 - Center
 1 - Front Right
 7 - Side Right
 3 - Rear Right
 2 - Rear Left
 6 - Side Left
...

on my reference monitor with stereo speakers, only the front left and right make a noise.

I hooked it up to a bigger TV with the 5.1 amp on an optical link. It acted the same, cycling through all 8 channels but only making the hiss on the front left and right.

So it's closer but not there yet.

[Mans Rullgard (mansr)]

I presume your optical link is S/PDIF, which supports only two channels of PCM, so unless the audio is being compressed (e.g. as Dolby Digital) on the fly, the sender (in this case the TV) must downmix to stereo or simply drop the extra channels. I wouldn't be very surprised if the TV is simply dropping the high channels. I would have tested this using an amp with HDMI input.

[warmcat (andy-warmcat)]

I see, thanks for the information.

I look around for hdmi input amp but none existed in guanghua.

If anyone, maybe op has a 4430, tilt-tracking has this stuff and is working well using omap_5430evm_defconfig

 http://git.linaro.org/gitweb?p=landing-teams/working/ti/kernel.git;a=summary