[alsa-devel] [PATCH RFC v2 10/13] sound/core: add DRM ELD helper
Russell King - ARM Linux
linux at arm.linux.org.uk
Fri May 8 15:27:01 CEST 2015
On Fri, May 08, 2015 at 04:16:08PM +0300, Jyri Sarha wrote:
> On 2015-04-02 12:22, Russell King wrote:
> >+static const unsigned int eld_rates[] = {
> >+ 32000,
> >+ 44100,
> >+ 48000,
> >+ 88200,
> >+ 96000,
> >+ 176400,
> >+ 192000,
> >+};
> >+
>
> For what I can see, you are setting the cross dependency between
> the sample rate and channels incorrectly.
There is a dependency between sample rate and channels.
> You should look for the
> currently tested channel count directly from hw params.
I'm not so sure that's right after looking at snd_ac97_pcm_double_rate_rules().
That's pretty much the same problem - AC'97 codecs can operate at a
sample rate of either the bus frame frequency or twice the bus frame
frequency.
They achieve twice the bus frame frequency by reallocating a couple
of the PCM data slots which would otherwise be used for >2 channels
to the first two channels, thus allowing two front channel samples
per frame.
AC'97 limits the number of channels to two if:
if (rate->min > 48000) {
and limits the sample rate to 1-48kHz if:
if (channels->min > 2) {
> From this side the dependency is missing all together.
Yes, it I initially couldn't work out how to do that bit... but I have
a solution now which seems to sort-of work.
Testing with aplay, I find that it seems to mostly work, and I guess
that:
aplay -D hw:0,0 -v -f S24_LE -c 6 -r 192000 /dev/zero
resulting in:
Playing raw data '/dev/zero' : Signed 24 bit Little Endian, Rate 192000 Hz, Channels 6
Warning: rate is not accurate (requested = 192000Hz, got = 48000Hz)
please, try the plug plugin
Hardware PCM card 0 'DW-HDMI' device 0 subdevice 0
Its setup is:
stream : PLAYBACK
access : RW_INTERLEAVED
format : S24_LE
subformat : STD
channels : 6
rate : 48000
exact rate : 48000 (48000/1)
is acceptable.
Also looking at AC'97, I don't need to list the same parameter as a
dependent of the rule... something I'll try when I'm back from the
hospital later this afternoon...
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
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