On 11.01.2011 19:41, Stephen Warren wrote:
Anssi Hannula wrote:
On 10.01.2011 18:19, Nitin Daga wrote:
Added hardware constraint in patch_hdmi.c to disable channels 4/6 which are not supported by some older NVIDIA GPUs.
And 3/5/7, which do not seem to work either with my 0x0007.
Are 3/5/7 channels supported by any vendor?
However, 3/5/7 do not work with my 0x000b system either, is this a hw limitation as well (that should be added to the driver) or is there a bug in the HDA driver for uneven channel counts?
I don't know if NVIDIA HW supports odd numbers of channels; Nitin, can you please find out? That said, the error you quote below for 5 channels sounds more like a software issue to me; some kind of buffer alignment or size constraint can't be satisfied?
(I looked at the HDA specification and it does seem to allow odd-numbered channel counts)
I skimmed quickly, and the only reference I could find was in section 7.6 "Audio Data Packetization" of HDMISpecification1.4a.pdf:
Layout 1 can be used to carry one audio sample with three to eight channels of L-PCM audio.... which implies support for an odd number of channels.
That said, the tables and other text near that quote indicate that audio is transferred in subpackets which each contain a pair of channels, and the sample_present bits each cover a subpacket, i.e. a pair of channels. Perhaps table 5-13 "Audio Sample Subpacket"'s V.L/V.R (channel validity) bits are intended to represent which of the two channels in a subpacket exist?
Well, the channel is certainly not valid if it does not exist :) But I don't think it is that field.
Looking at CEA-861D, Table 17 "Audio InfoFrame Data Byte 1", CC (Channel Count) bits, it's quite explicit that odd numbers of channels are supported.
Actually, I just tested and just transmitting 3-channel data with extra 4th dummy channel while setting the Audio InfoFrame fields to indicate a 3 channel stream makes it work.
So it would seem (to me) like the best approach would be: 1. Add a hw_constraint to prevent odd channel counts (easy) 2. Provide some way for alsa plug (and the user application) to indicate the "actual/original" channel count/layout without dummy channels, so that the infoframe can be set correctly. This is harder, and I guess should probably be implemented so that the channel remapping issue on older nvidia hw will be fixed as well.
Strangely, on both of my systems speaker-test -c5 fails with an error:
$ speaker-test -Dhdmi -c5
speaker-test 1.0.23
Playback device is hdmi Stream parameters are 48000Hz, S16_LE, 5 channels Using 16 octaves of pink noise Rate set to 48000Hz (requested 48000Hz) Buffer size range from 128 to 419392 Period size range from 64 to 209664 Using max buffer size 419392 Periods = 4 Unable to set nperiods 4 for playback: No such file or directory Setting of hwparams failed: No such file or directory
While -c3 and -c7 run fine but no sound is received.
[Nitin's patch elided]