Takashi Iwai wrote:
> At Thu, 13 Mar 2008 13:49:20 +0100,
> Pavel Hofman wrote:
>> Takashi Iwai napsal(a):
>>> 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.
>>>
>>>
>> Well, I would not want to skip the check for cards with functioning rate
>> detection. Plus snd_ak4114_check_rate_and_errors gets called
>> periodically afterwards.
>
> Yes, but the check there is simply useless at open. It's only for
> running states. snd_ak4114_external_rate() would be simler, then.
>
>> It would be great if the driver in slaved-clock mode cut its list of
>> native sample rates to the only one currently fed to SPDIF input and
>> detected by AK4114. A routine doing this would be called when switching
>> clock to the slaved-clock mode and called again in
>> snd_ak4114_check_rate_and_errors() when any change in input rate is
>> detected (and the stream is not running). Going back to master-clock
>> mode would restore the existing list of all the rates.
>>
>> In case of input sample rate change when the PCM stream is running, the
>> stream would be stopped. This is already implemented in the current
>> version of snd_ak4114_check_rate_and_errors()
>>
>> Unfortunately, I do not know how to change the rates list properly not
>> to break something. If it is only about changing the HW params struct,
>> that would be trivial.
>
> Suppose that the slave <-> master mode change doesn't happen during
> the stream is opened, it's relatively easy. So far, ice1724.c doesn't
> call spdif.ops.open/close callbacks. Call them in *_spdif_open/close
> functions with NULL check. Then add open hook in juli.c so that you
> can change rates_min and rates_max to the currently detected rate at
> open...
>
> Well, it's faster to write a patch than texts.
>
>
.......
Takashi, thanks for the patch, it works flawlessly.
Another issue - when the external clock changes rate and the stream is
running (typically when starting the source playback which switches the
source card (and its SPDIF-OUT) to a different frequency), the target
card detects the change and the capture stream is stopped in
snd_ak4114_check_rate_and_errors() by
snd_pcm_stop(ak4114->capture_substream, SNDRV_PCM_STATE_DRAINING);
How should recording applications behave with stream in this mode? I
would expect arecord to close, but it does nothing. Is this correct
behaviour?
Thanks,
Pavel.
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