At Wed, 12 Mar 2008 23:50:08 +0100, Pavel Hofman wrote:
Hi,
here is my scenario:
ICE1724 card, trying to record from SPDIF input via AK4114, ICE1724 slaved to SPDIF clock from the receiver.
The card detects SPDIF input rate correctly (in my case ESI Juli where AK4114 is provided with independent clock signal to enable the rate detection). Let's say it is 192000.
Now I want to arecord the input stream, let's say in CD quality, using the plug plugin. The command fails, because of the check in ak4114.c:
res = external_rate(rcs1); if (!(flags & AK4114_CHECK_NO_RATE) && runtime && runtime->rate != res) { snd_pcm_stream_lock_irqsave(ak4114->capture_substream, _flags); if (snd_pcm_running(ak4114->capture_substream)) { printk(KERN_DEBUG "rate changed (%i <- %i)\n", runtime->rate, res); snd_pcm_stop(ak4114->capture_substream, SNDRV_PCM_STATE_DRAINING); res = 1; } snd_pcm_stream_unlock_irqrestore(ak4114->capture_substream, _flags); }
The stream gets stopped because res = 192000 and runtime->rate = 44100.
The problem is that the capture device still offers all the available rates, instead of the single SPDIF input one. Thus, the plug plugin is not forced to convert from 192000 to 44100 and runtime->rate is 44100 instead of 192000.
Of course recording at 192000 works fine.
What would be the best way to force the SPDIF capture device to offer (advertise) only the current rate? This functionality would have to be applicable only to the few cards correctly detecting incoming rate (unlike most ice1724 cards without independent clock in slave mode).
What about to call snd_ak4114_check_rate_and_errors() at PCM open? You can pass AK4114_CHECK_NO_RATE to flags argument to skip the check there, at least.
Takashi