period_time in slave definition

period_time in slave definition

[Pavel Hofman]

Hi,

According to
http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html , my
.asoundrc contains:

pcm.test {
        type plug
        slave {
                pcm "hw:0"
                format "unchanged"
                channels "unchanged"
                rate "unchanged"
                period_size 1024
                buffer_size 4096
        }
}


While pcm, format, channels, and rate are accepted, the period and
buffer fields are refused:

ALSA lib pcm.c:6811:(snd_pcm_slave_conf) Unknown field period_time

I checked the source code and the keywords seem to be ok

pcm.c:
static const char *const names[SND_PCM_HW_PARAM_LAST_INTERVAL + 1] = {
	[SND_PCM_HW_PARAM_FORMAT] = "format",
	[SND_PCM_HW_PARAM_CHANNELS] = "channels",
	[SND_PCM_HW_PARAM_RATE] = "rate",
	[SND_PCM_HW_PARAM_PERIOD_TIME] = "period_time",
	[SND_PCM_HW_PARAM_PERIOD_SIZE] = "period_size",
	[SND_PCM_HW_PARAM_BUFFER_TIME] = "buffer_time",
	[SND_PCM_HW_PARAM_BUFFER_SIZE] = "buffer_size",
	[SND_PCM_HW_PARAM_PERIODS] = "periods"
};


Has any change been introduced recently which is not reflected on wiki
yet? Is there a way to specify "default" period and buffer parameters?

Thanks a lot,

Pavel.

Re: period_time in slave definition

[Jaroslav Kysela]

On Mon, 28 Feb 2011, Pavel Hofman wrote:

> Hi,
>
> According to
> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html , my
> .asoundrc contains:
>
> pcm.test {
>        type plug
>        slave {
>                pcm "hw:0"
>                format "unchanged"
>                channels "unchanged"
>                rate "unchanged"
>                period_size 1024
>                buffer_size 4096
>        }
> }
>
>
> While pcm, format, channels, and rate are accepted, the period and
> buffer fields are refused:
>
> ALSA lib pcm.c:6811:(snd_pcm_slave_conf) Unknown field period_time

It's correct, pcm:plug does not support buffer modifiers. Look to 
"Automatic conversion plugin".

> I checked the source code and the keywords seem to be ok
>
> pcm.c:
> static const char *const names[SND_PCM_HW_PARAM_LAST_INTERVAL + 1] = {
> 	[SND_PCM_HW_PARAM_FORMAT] = "format",
> 	[SND_PCM_HW_PARAM_CHANNELS] = "channels",
> 	[SND_PCM_HW_PARAM_RATE] = "rate",
> 	[SND_PCM_HW_PARAM_PERIOD_TIME] = "period_time",
> 	[SND_PCM_HW_PARAM_PERIOD_SIZE] = "period_size",
> 	[SND_PCM_HW_PARAM_BUFFER_TIME] = "buffer_time",
> 	[SND_PCM_HW_PARAM_BUFFER_SIZE] = "buffer_size",
> 	[SND_PCM_HW_PARAM_PERIODS] = "periods"
> };

It's just a table to translate all possibilites between index and name. 
The plug plugins allow only this:

 	err = snd_pcm_slave_conf(root, slave, &sconf, 3,
 				 SND_PCM_HW_PARAM_FORMAT, SCONF_UNCHANGED, &sformat,
 				 SND_PCM_HW_PARAM_CHANNELS, SCONF_UNCHANGED, &schannels,
 				 SND_PCM_HW_PARAM_RATE, SCONF_UNCHANGED, &srate);

 					Jaroslav

-----
Jaroslav Kysela <perex@perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

Re: period_time in slave definition

[Pavel Hofman]

Jaroslav Kysela napsal(a):
> On Mon, 28 Feb 2011, Pavel Hofman wrote:
> 
>> Hi,
>>
>> According to
>> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html , my
>> .asoundrc contains:
>>
>> pcm.test {
>>        type plug
>>        slave {
>>                pcm "hw:0"
>>                format "unchanged"
>>                channels "unchanged"
>>                rate "unchanged"
>>                period_size 1024
>>                buffer_size 4096
>>        }
>> }
>>
>>
>> While pcm, format, channels, and rate are accepted, the period and
>> buffer fields are refused:
>>
>> ALSA lib pcm.c:6811:(snd_pcm_slave_conf) Unknown field period_time
> 
> It's correct, pcm:plug does not support buffer modifiers. Look to
> "Automatic conversion plugin".
> 
>> I checked the source code and the keywords seem to be ok
>>
>> pcm.c:
>> static const char *const names[SND_PCM_HW_PARAM_LAST_INTERVAL + 1] = {
>>     [SND_PCM_HW_PARAM_FORMAT] = "format",
>>     [SND_PCM_HW_PARAM_CHANNELS] = "channels",
>>     [SND_PCM_HW_PARAM_RATE] = "rate",
>>     [SND_PCM_HW_PARAM_PERIOD_TIME] = "period_time",
>>     [SND_PCM_HW_PARAM_PERIOD_SIZE] = "period_size",
>>     [SND_PCM_HW_PARAM_BUFFER_TIME] = "buffer_time",
>>     [SND_PCM_HW_PARAM_BUFFER_SIZE] = "buffer_size",
>>     [SND_PCM_HW_PARAM_PERIODS] = "periods"
>> };
> 
> It's just a table to translate all possibilites between index and name.
> The plug plugins allow only this:
> 
>     err = snd_pcm_slave_conf(root, slave, &sconf, 3,
>                  SND_PCM_HW_PARAM_FORMAT, SCONF_UNCHANGED, &sformat,
>                  SND_PCM_HW_PARAM_CHANNELS, SCONF_UNCHANGED, &schannels,
>                  SND_PCM_HW_PARAM_RATE, SCONF_UNCHANGED, &srate);
> 
>                     Jaroslav
> 

Thanks a lot for your response. Is there a way to set default
period/buffer parameters for applications which do not specify them
(i.e. audacious)? My idea was to put it somewhere into device definition
in .asoundrc. Dmix is not used.

Thanks,

Pavel.

Re: period_time in slave definition

[Pavel Hofman]

Jaroslav Kysela napsal(a):
> On Mon, 28 Feb 2011, Pavel Hofman wrote:
> 
>> Hi,
>>
>> According to
>> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html , my
>> .asoundrc contains:
>>
>> pcm.test {
>>        type plug
>>        slave {
>>                pcm "hw:0"
>>                format "unchanged"
>>                channels "unchanged"
>>                rate "unchanged"
>>                period_size 1024
>>                buffer_size 4096
>>        }
>> }
>>
>>
>> While pcm, format, channels, and rate are accepted, the period and
>> buffer fields are refused:
>>
>> ALSA lib pcm.c:6811:(snd_pcm_slave_conf) Unknown field period_time
> 
> It's correct, pcm:plug does not support buffer modifiers. Look to
> "Automatic conversion plugin".
> 
>> I checked the source code and the keywords seem to be ok
>>
>> pcm.c:
>> static const char *const names[SND_PCM_HW_PARAM_LAST_INTERVAL + 1] = {
>>     [SND_PCM_HW_PARAM_FORMAT] = "format",
>>     [SND_PCM_HW_PARAM_CHANNELS] = "channels",
>>     [SND_PCM_HW_PARAM_RATE] = "rate",
>>     [SND_PCM_HW_PARAM_PERIOD_TIME] = "period_time",
>>     [SND_PCM_HW_PARAM_PERIOD_SIZE] = "period_size",
>>     [SND_PCM_HW_PARAM_BUFFER_TIME] = "buffer_time",
>>     [SND_PCM_HW_PARAM_BUFFER_SIZE] = "buffer_size",
>>     [SND_PCM_HW_PARAM_PERIODS] = "periods"
>> };
> 
> It's just a table to translate all possibilites between index and name.
> The plug plugins allow only this:
> 
>     err = snd_pcm_slave_conf(root, slave, &sconf, 3,
>                  SND_PCM_HW_PARAM_FORMAT, SCONF_UNCHANGED, &sformat,
>                  SND_PCM_HW_PARAM_CHANNELS, SCONF_UNCHANGED, &schannels,
>                  SND_PCM_HW_PARAM_RATE, SCONF_UNCHANGED, &srate);
> 
>                     Jaroslav
> 


Well, still I do not understand why we are talking about the plug
plugin, when I am trying to redefine the slave via pcm_slave. The
documentation at
http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html says the
pcm_slave can define period_time and buffer_time, while a slightly
modified example from the wiki page fails:

pcm_slave.slave_rate44100Hz {
        pcm "hw:0,0"
        rate 44100
--->	period_time 1024	
}

pcm.rate44100Hz {
        type plug
        slave slave_rate44100Hz
}

How does the slave definition relate to the plug plugin? Sorry for these
basics but I am really trying to understand that, so far no success.

Thanks a lot.

Pavel.

Re: period_time in slave definition

[Jaroslav Kysela]

On Tue, 1 Mar 2011, Pavel Hofman wrote:

> Jaroslav Kysela napsal(a):
>> On Mon, 28 Feb 2011, Pavel Hofman wrote:
>>
>>> Hi,
>>>
>>> According to
>>> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html , my
>>> .asoundrc contains:
>>>
>>> pcm.test {
>>>        type plug
>>>        slave {
>>>                pcm "hw:0"
>>>                format "unchanged"
>>>                channels "unchanged"
>>>                rate "unchanged"
>>>                period_size 1024
>>>                buffer_size 4096
>>>        }
>>> }
>>>
>>>
>>> While pcm, format, channels, and rate are accepted, the period and
>>> buffer fields are refused:
>>>
>>> ALSA lib pcm.c:6811:(snd_pcm_slave_conf) Unknown field period_time
>>
>> It's correct, pcm:plug does not support buffer modifiers. Look to
>> "Automatic conversion plugin".
>>
>>> I checked the source code and the keywords seem to be ok
>>>
>>> pcm.c:
>>> static const char *const names[SND_PCM_HW_PARAM_LAST_INTERVAL + 1] = {
>>>     [SND_PCM_HW_PARAM_FORMAT] = "format",
>>>     [SND_PCM_HW_PARAM_CHANNELS] = "channels",
>>>     [SND_PCM_HW_PARAM_RATE] = "rate",
>>>     [SND_PCM_HW_PARAM_PERIOD_TIME] = "period_time",
>>>     [SND_PCM_HW_PARAM_PERIOD_SIZE] = "period_size",
>>>     [SND_PCM_HW_PARAM_BUFFER_TIME] = "buffer_time",
>>>     [SND_PCM_HW_PARAM_BUFFER_SIZE] = "buffer_size",
>>>     [SND_PCM_HW_PARAM_PERIODS] = "periods"
>>> };
>>
>> It's just a table to translate all possibilites between index and name.
>> The plug plugins allow only this:
>>
>>     err = snd_pcm_slave_conf(root, slave, &sconf, 3,
>>                  SND_PCM_HW_PARAM_FORMAT, SCONF_UNCHANGED, &sformat,
>>                  SND_PCM_HW_PARAM_CHANNELS, SCONF_UNCHANGED, &schannels,
>>                  SND_PCM_HW_PARAM_RATE, SCONF_UNCHANGED, &srate);
>>
>>                     Jaroslav
>>
>
>
> Well, still I do not understand why we are talking about the plug
> plugin, when I am trying to redefine the slave via pcm_slave. The
> documentation at
> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html says the
> pcm_slave can define period_time and buffer_time, while a slightly
> modified example from the wiki page fails:
>
> pcm_slave.slave_rate44100Hz {
>        pcm "hw:0,0"
>        rate 44100
> --->	period_time 1024
> }
>
> pcm.rate44100Hz {
>        type plug
>        slave slave_rate44100Hz
> }
>
> How does the slave definition relate to the plug plugin? Sorry for these
> basics but I am really trying to understand that, so far no success.

The above description is an universal description for all slaves. 
Unfortunately, not all plugins accept the whole range of parameters.
You have to look to the snd_pcm_slave_conf() caller which parameters are 
accepted.

The description should be better.

 					Jaroslav

-----
Jaroslav Kysela <perex@perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

Re: period_time in slave definition

[Pavel Hofman]

Jaroslav Kysela napsal(a):
> On Tue, 1 Mar 2011, Pavel Hofman wrote:
> 
>> Jaroslav Kysela napsal(a):
>>>
>>> It's correct, pcm:plug does not support buffer modifiers. Look to
>>> "Automatic conversion plugin".
>>>
>>>> I checked the source code and the keywords seem to be ok
>>>>
>>>> pcm.c:
>>>> static const char *const names[SND_PCM_HW_PARAM_LAST_INTERVAL + 1] = {
>>>>     [SND_PCM_HW_PARAM_FORMAT] = "format",
>>>>     [SND_PCM_HW_PARAM_CHANNELS] = "channels",
>>>>     [SND_PCM_HW_PARAM_RATE] = "rate",
>>>>     [SND_PCM_HW_PARAM_PERIOD_TIME] = "period_time",
>>>>     [SND_PCM_HW_PARAM_PERIOD_SIZE] = "period_size",
>>>>     [SND_PCM_HW_PARAM_BUFFER_TIME] = "buffer_time",
>>>>     [SND_PCM_HW_PARAM_BUFFER_SIZE] = "buffer_size",
>>>>     [SND_PCM_HW_PARAM_PERIODS] = "periods"
>>>> };
>>>
>>> It's just a table to translate all possibilites between index and name.
>>> The plug plugins allow only this:
>>>
>>>     err = snd_pcm_slave_conf(root, slave, &sconf, 3,
>>>                  SND_PCM_HW_PARAM_FORMAT, SCONF_UNCHANGED, &sformat,
>>>                  SND_PCM_HW_PARAM_CHANNELS, SCONF_UNCHANGED, &schannels,
>>>                  SND_PCM_HW_PARAM_RATE, SCONF_UNCHANGED, &srate);
>>>
>>>                     Jaroslav
>>>
>>
>>
>> Well, still I do not understand why we are talking about the plug
>> plugin, when I am trying to redefine the slave via pcm_slave. The
>> documentation at
>> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html says the
>> pcm_slave can define period_time and buffer_time, while a slightly
>> modified example from the wiki page fails:
>>
>> pcm_slave.slave_rate44100Hz {
>>        pcm "hw:0,0"
>>        rate 44100
>> --->    period_time 1024
>> }
>>
>> pcm.rate44100Hz {
>>        type plug
>>        slave slave_rate44100Hz
>> }
>>
>> How does the slave definition relate to the plug plugin? Sorry for these
>> basics but I am really trying to understand that, so far no success.
> 
> The above description is an universal description for all slaves.
> Unfortunately, not all plugins accept the whole range of parameters.
> You have to look to the snd_pcm_slave_conf() caller which parameters are
> accepted.
> 

Thanks a lot for your clarification. Would it make sense to add these
parameters to the plug plugin? I guess it would not be as simple as in
dshare.c:

	params.period_size = psize;
	params.buffer_size = bsize;

when opening the slave.

Or should I use dshare when I need to specify period and buffer
parameters outside of the application?

Thanks a lot,

Pavel.

Re: period_time in slave definition

[Pavel Hofman]

Pavel Hofman napsal(a):
> Jaroslav Kysela napsal(a):
>> On Tue, 1 Mar 2011, Pavel Hofman wrote:
>>
>>> Jaroslav Kysela napsal(a):
>>>> It's correct, pcm:plug does not support buffer modifiers. Look to
>>>> "Automatic conversion plugin".
>>>>
>>>>> I checked the source code and the keywords seem to be ok
>>>>>
>>>>> pcm.c:
>>>>> static const char *const names[SND_PCM_HW_PARAM_LAST_INTERVAL + 1] = {
>>>>>     [SND_PCM_HW_PARAM_FORMAT] = "format",
>>>>>     [SND_PCM_HW_PARAM_CHANNELS] = "channels",
>>>>>     [SND_PCM_HW_PARAM_RATE] = "rate",
>>>>>     [SND_PCM_HW_PARAM_PERIOD_TIME] = "period_time",
>>>>>     [SND_PCM_HW_PARAM_PERIOD_SIZE] = "period_size",
>>>>>     [SND_PCM_HW_PARAM_BUFFER_TIME] = "buffer_time",
>>>>>     [SND_PCM_HW_PARAM_BUFFER_SIZE] = "buffer_size",
>>>>>     [SND_PCM_HW_PARAM_PERIODS] = "periods"
>>>>> };
>>>> It's just a table to translate all possibilites between index and name.
>>>> The plug plugins allow only this:
>>>>
>>>>     err = snd_pcm_slave_conf(root, slave, &sconf, 3,
>>>>                  SND_PCM_HW_PARAM_FORMAT, SCONF_UNCHANGED, &sformat,
>>>>                  SND_PCM_HW_PARAM_CHANNELS, SCONF_UNCHANGED, &schannels,
>>>>                  SND_PCM_HW_PARAM_RATE, SCONF_UNCHANGED, &srate);
>>>>
>>>>                     Jaroslav
>>>>
>>>
>>> Well, still I do not understand why we are talking about the plug
>>> plugin, when I am trying to redefine the slave via pcm_slave. The
>>> documentation at
>>> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html says the
>>> pcm_slave can define period_time and buffer_time, while a slightly
>>> modified example from the wiki page fails:
>>>
>>> pcm_slave.slave_rate44100Hz {
>>>        pcm "hw:0,0"
>>>        rate 44100
>>> --->    period_time 1024
>>> }
>>>
>>> pcm.rate44100Hz {
>>>        type plug
>>>        slave slave_rate44100Hz
>>> }
>>>
>>> How does the slave definition relate to the plug plugin? Sorry for these
>>> basics but I am really trying to understand that, so far no success.
>> The above description is an universal description for all slaves.
>> Unfortunately, not all plugins accept the whole range of parameters.
>> You have to look to the snd_pcm_slave_conf() caller which parameters are
>> accepted.
>>
> 
> Thanks a lot for your clarification. Would it make sense to add these
> parameters to the plug plugin? I guess it would not be as simple as in
> dshare.c:
> 
> 	params.period_size = psize;
> 	params.buffer_size = bsize;
> 
> when opening the slave.
> 
> Or should I use dshare when I need to specify period and buffer
> parameters outside of the application?
> 

Well, dshare resamples to common rate too. That is not the way to go.

Thanks,

Pavel.

Re: period_time in slave definition

[Pavel Hofman]

Pavel Hofman napsal(a):
> Jaroslav Kysela napsal(a):
>> On Tue, 1 Mar 2011, Pavel Hofman wrote:
>>
>>> Jaroslav Kysela napsal(a):
>>>> It's correct, pcm:plug does not support buffer modifiers. Look to
>>>> "Automatic conversion plugin".
>>>>
>>>>> I checked the source code and the keywords seem to be ok
>>>>>
>>>>> pcm.c:
>>>>> static const char *const names[SND_PCM_HW_PARAM_LAST_INTERVAL + 1] = {
>>>>>     [SND_PCM_HW_PARAM_FORMAT] = "format",
>>>>>     [SND_PCM_HW_PARAM_CHANNELS] = "channels",
>>>>>     [SND_PCM_HW_PARAM_RATE] = "rate",
>>>>>     [SND_PCM_HW_PARAM_PERIOD_TIME] = "period_time",
>>>>>     [SND_PCM_HW_PARAM_PERIOD_SIZE] = "period_size",
>>>>>     [SND_PCM_HW_PARAM_BUFFER_TIME] = "buffer_time",
>>>>>     [SND_PCM_HW_PARAM_BUFFER_SIZE] = "buffer_size",
>>>>>     [SND_PCM_HW_PARAM_PERIODS] = "periods"
>>>>> };
>>>> It's just a table to translate all possibilites between index and name.
>>>> The plug plugins allow only this:
>>>>
>>>>     err = snd_pcm_slave_conf(root, slave, &sconf, 3,
>>>>                  SND_PCM_HW_PARAM_FORMAT, SCONF_UNCHANGED, &sformat,
>>>>                  SND_PCM_HW_PARAM_CHANNELS, SCONF_UNCHANGED, &schannels,
>>>>                  SND_PCM_HW_PARAM_RATE, SCONF_UNCHANGED, &srate);
>>>>
>>>>                     Jaroslav
>>>>
>>>
>>> Well, still I do not understand why we are talking about the plug
>>> plugin, when I am trying to redefine the slave via pcm_slave. The
>>> documentation at
>>> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html says the
>>> pcm_slave can define period_time and buffer_time, while a slightly
>>> modified example from the wiki page fails:
>>>
>>> pcm_slave.slave_rate44100Hz {
>>>        pcm "hw:0,0"
>>>        rate 44100
>>> --->    period_time 1024
>>> }
>>>
>>> pcm.rate44100Hz {
>>>        type plug
>>>        slave slave_rate44100Hz
>>> }
>>>
>>> How does the slave definition relate to the plug plugin? Sorry for these
>>> basics but I am really trying to understand that, so far no success.
>> The above description is an universal description for all slaves.
>> Unfortunately, not all plugins accept the whole range of parameters.
>> You have to look to the snd_pcm_slave_conf() caller which parameters are
>> accepted.
>>
> 
> Thanks a lot for your clarification. Would it make sense to add these
> parameters to the plug plugin? I guess it would not be as simple as in
> dshare.c:
> 
> 	params.period_size = psize;
> 	params.buffer_size = bsize;
> 
> when opening the slave.
> 

One more question regarding the defaults. Older version of audacious
(e.g. in ubuntu karmic) uses a very simple code:

    snd_pcm_hw_params_alloca(&hwparams);
    snd_pcm_hw_params_any(pcm_handle, hwparams);
    snd_pcm_hw_params_set_access(pcm_handle, hwparams,
SND_PCM_ACCESS_RW_INTERLEAVED);
    snd_pcm_hw_params_set_format(pcm_handle, hwparams, afmt);
    snd_pcm_hw_params_set_channels(pcm_handle, hwparams, nch);
    snd_pcm_hw_params_set_rate(pcm_handle, hwparams, rate, 0);

    err = snd_pcm_hw_params(pcm_handle, hwparams);
    if (err < 0)
    {
        _ERROR("snd_pcm_hw_params failed: %s", snd_strerror(err));
        return -1;
    }


There is no buffer or period setup. I assume some alsa-lib default value
is used. When playing, the period size is set very low:

access: MMAP_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 96000 (96000/1)
period_size: 8
buffer_size: 8192

As a result, the sound card (ICH5) keeps throwing 12.000 interrupts per
second and CPU load is rather high. Does this "default" period_size
value make sense? This is the reason I am trying to specify it outside
of the application.

Thanks a lot for help.

Pavel.