Problem writing to PCM plugin

Problem writing to PCM plugin

[Arve Knudsen]

I'm currently trying to implement support for user defined pcm plugins in  
PortAudio ALSA (ALSA-lib 1.05), and I've got as far as discovering the  
pcms. In order to test I defined a routing plugin, which moves data from  
channel 0/1 to 16/17 (S/PDIF) on my Hammerfall Lite. With aplay this  
plugin works just fine, but when I open it with PortAudio the same way as  
with any hardware device, the output is simply silent (I can't listen to  
any of the ADAT channels since I lack ADAT gear). Defining a simple plugin  
which does nothing but drive my onboard nForce2 (routing fails with this  
assertion: 'pcm_plug.c:363: snd_pcm_plug_change_channels: Assertion  
`snd_pcm_format_linear(slv->format)' failed') works the same as if I open  
the hw device.

The obvious difference to aplay I can think of is that we use floating  
point format in the PortAudio tests, so there is an intermediate  
conversion before the audio gets to the routing plugin. Could this be the  
cause of the problem? If you wish I can provide output from snd_pcm_dump.

Thanks

Arve Knudsen


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Re: Problem writing to PCM plugin

[Jaroslav Kysela]

On Wed, 11 Aug 2004, Arve Knudsen wrote:

> point format in the PortAudio tests, so there is an intermediate  
> conversion before the audio gets to the routing plugin. Could this be the  
> cause of the problem? If you wish I can provide output from snd_pcm_dump.

Yes, send the dump, please.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs


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Re: Problem writing to PCM plugin

[Arve Knudsen]

The plugin:
pcm.9636SPDIF {
     type plug
     slave.pcm "hw:1"
     ttable.0.16 1
     ttable.1.17 1
}

The dump:
Plug PCM: Linear Integer <-> Linear Float conversion PCM (S32_LE)
Its setup is:
stream       : PLAYBACK
access       : MMAP_INTERLEAVED
format       : FLOAT_LE
subformat    : STD
channels     : 2
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 32
buffer_size  : 2048
period_size  : 1024
period_time  : 23219
tick_time    : 1000
tstamp_mode  : MMAP
period_step  : 1
sleep_min    : 0
avail_min    : 1024
xfer_align   : 1
start_threshold  : 1024
stop_threshold   : 2048
silence_threshold: 0
silence_size : 2147483647
boundary     : 1073741824
Slave: Route conversion PCM (sformat=S32_LE)
Transformation table:
0 <- none
1 <- none
Its setup is:
stream       : PLAYBACK
access       : MMAP_INTERLEAVED
format       : S32_LE
subformat    : STD
channels     : 2
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 32
buffer_size  : 2048
period_size  : 1024
period_time  : 23219
tick_time    : 1000
tstamp_mode  : MMAP
period_step  : 1
sleep_min    : 0
avail_min    : 1024
xfer_align   : 1
start_threshold  : 1024
stop_threshold   : 2048
silence_threshold: 0
silence_size : 2147483647
boundary     : 1073741824
Slave: Route conversion PCM (sformat=S32_LE)
Transformation table:
0 <- none
1 <- none
2 <- none
3 <- none
4 <- none
5 <- none
6 <- none
7 <- none
8 <- none
9 <- none
10 <- none
11 <- none
12 <- none
13 <- none
14 <- none
15 <- none
16 <- 0
17 <- 1
Its setup is:
stream       : PLAYBACK
access       : MMAP_INTERLEAVED
format       : S32_LE
subformat    : STD
channels     : 2
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 32
buffer_size  : 2048
period_size  : 1024
period_time  : 23219
tick_time    : 1000
tstamp_mode  : MMAP
period_step  : 1
sleep_min    : 0
avail_min    : 1024
xfer_align   : 1
start_threshold  : 1024
stop_threshold   : 2048
silence_threshold: 0
silence_size : 2147483647
boundary     : 1073741824
Slave: Hardware PCM card 1 'RME Digi9636 (Rev 1.5)' device 0 subdevice 0

Its setup is:
stream       : PLAYBACK
access       : MMAP_NONINTERLEAVED
format       : S32_LE
subformat    : STD
channels     : 18
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 24
buffer_size  : 2048
period_size  : 1024
period_time  : 23219
tick_time    : 1000
tstamp_mode  : MMAP
period_step  : 1
sleep_min    : 0
avail_min    : 1024
xfer_align   : 1
start_threshold  : 1024
stop_threshold   : 2048
silence_threshold: 0
silence_size : 2147483647
boundary     : 1073741824

On Wed, 11 Aug 2004 15:36:24 +0200 (CEST), Jaroslav Kysela <perex@suse.cz>  
wrote:

> On Wed, 11 Aug 2004, Arve Knudsen wrote:
>
>> point format in the PortAudio tests, so there is an intermediate
>> conversion before the audio gets to the routing plugin. Could this be  
>> the
>> cause of the problem? If you wish I can provide output from  
>> snd_pcm_dump.
>
> Yes, send the dump, please.
>
> 						Jaroslav
>
> -----
> Jaroslav Kysela <perex@suse.cz>
> Linux Kernel Sound Maintainer
> ALSA Project, SUSE Labs




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Re: Problem writing to PCM plugin

[Clemens Ladisch]

Arve Knudsen wrote:
> pcm_plug.c:363: snd_pcm_plug_change_channels: Assertion
> `snd_pcm_format_linear(slv->format)' failed'
>
> The obvious difference to aplay I can think of is that we use floating
> point format in the PortAudio tests, so there is an intermediate
> conversion before the audio gets to the routing plugin.

The route plugin doesn't support floating point formats.  Try wrapping
it into a lfloat (or plug) plugin.


HTH
Clemens




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Re: Problem writing to PCM plugin

[Arve Knudsen]

Actually the plugin is of type "plug", and according to snd_pcm_dump it  
seems ALSA-lib takes care of converting the sample format. Only getting to  
know the plugin system here ...

Regards

Arve Knudsen

On Wed, 11 Aug 2004 15:45:29 +0200 (METDST), Clemens Ladisch  
<clemens@ladisch.de> wrote:

> Arve Knudsen wrote:
>> pcm_plug.c:363: snd_pcm_plug_change_channels: Assertion
>> `snd_pcm_format_linear(slv->format)' failed'
>>
>> The obvious difference to aplay I can think of is that we use floating
>> point format in the PortAudio tests, so there is an intermediate
>> conversion before the audio gets to the routing plugin.
>
> The route plugin doesn't support floating point formats.  Try wrapping
> it into a lfloat (or plug) plugin.
>
>
> HTH
> Clemens
>
>




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Re: Problem writing to PCM plugin

[Arve Knudsen]

Based on your suggestion I rewrote the plugin, so it wraps a route plugin.  
And now things work as I would expect. I must say I'm still confused on  
the issue, as I haven't found any explanation why my original approach  
wouldn't work. What's the difference between defining a translation table  
directly inside a "plug" plugin, and aggregating a slave "route" plugin  
within a "plug"?

Sort of weird that the plugin caused an assertion only when used in  
combination with the nForce2 chip, and not the Hammerfall (just silent  
operation).

Thanks

Arve Knudsen

On Wed, 11 Aug 2004 15:45:29 +0200 (METDST), Clemens Ladisch  
<clemens@ladisch.de> wrote:

> Arve Knudsen wrote:
>> pcm_plug.c:363: snd_pcm_plug_change_channels: Assertion
>> `snd_pcm_format_linear(slv->format)' failed'
>>
>> The obvious difference to aplay I can think of is that we use floating
>> point format in the PortAudio tests, so there is an intermediate
>> conversion before the audio gets to the routing plugin.
>
> The route plugin doesn't support floating point formats.  Try wrapping
> it into a lfloat (or plug) plugin.
>
>
> HTH
> Clemens
>
>
>
>
> -------------------------------------------------------
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Re: Problem writing to PCM plugin

[Jaroslav Kysela]

On Wed, 11 Aug 2004, Arve Knudsen wrote:

> Based on your suggestion I rewrote the plugin, so it wraps a route plugin.  
> And now things work as I would expect. I must say I'm still confused on  
> the issue, as I haven't found any explanation why my original approach  
> wouldn't work. What's the difference between defining a translation table  
> directly inside a "plug" plugin, and aggregating a slave "route" plugin  
> within a "plug"?

There was an error in the plug plugin - one route plugin was inserted by 
mistake. This patch will fix the wrong plug behaviour:

Index: pcm_plug.c
===================================================================
RCS file: /cvsroot/alsa/alsa-lib/src/pcm/pcm_plug.c,v
retrieving revision 1.126
diff -u -r1.126 pcm_plug.c
--- pcm_plug.c	19 Apr 2004 13:24:19 -0000	1.126
+++ pcm_plug.c	11 Aug 2004 15:06:02 -0000
@@ -53,7 +53,7 @@
 	int srate;
 	enum snd_pcm_plug_route_policy route_policy;
 	snd_pcm_route_ttable_entry_t *ttable;
-	int ttable_ok;
+	int ttable_ok, ttable_last;
 	unsigned int tt_ssize, tt_cused, tt_sused;
 } snd_pcm_plug_t;
 
@@ -361,7 +361,8 @@
 	snd_pcm_route_ttable_entry_t *ttable;
 	int err;
 	assert(snd_pcm_format_linear(slv->format));
-	if (clt->channels == slv->channels && !plug->ttable)
+	if (clt->channels == slv->channels &&
+	    (!plug->ttable || !plug->ttable_last))
 		return 0;
 	if (clt->rate != slv->rate &&
 	    clt->channels > slv->channels)
@@ -560,7 +561,7 @@
 	};
 	snd_pcm_plug_params_t p = *slave;
 	unsigned int k = 0;
-	plug->ttable_ok = 0;
+	plug->ttable_ok = plug->ttable_last = 0;
 	while (client->format != p.format ||
 	       client->channels != p.channels ||
 	       client->rate != p.rate ||
@@ -584,6 +585,7 @@
 	if (plug->ttable && !plug->ttable_ok) {
 		snd_pcm_t *new;
 		int err;
+		plug->ttable_last = 1;
 		err = snd_pcm_plug_change_channels(pcm, &new, client, &p);
 		if (err < 0) {
 			snd_pcm_plug_clear(pcm);

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs


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