[alsa-devel] [PATCH] PCM parameters in file plugin

Pavel Hofman pavel.hofman at insite.cz
Mon Jan 19 23:20:49 CET 2009

Pavel Hofman wrote:
> Jaroslav Kysela wrote:
>> On Tue, 6 Jan 2009, Pavel Hofman wrote:
>>> Pavel Hofman napsal(a):
>>>> Hello,
>>>> I am working on a file plugin patch to allow adding PCM parameters 
>>>> (rate, format) to  the name of the file created (plus the ability to 
>>>> run an external command via popen, such as upsampling with sox). I 
>>>> got stuck in trying to obtain these parameters in 
>>>> pcm_file.c:_snd_pcm_file_open(). Is it actually possible or the 
>>>> information is not available at the time of opening the file (and 
>>>> the whole patch is thus nonsense)?
>>>> Thanks a lot for help.
>>> I am now opening the output file in pcm_file.c:snd_pcm_file_write_bytes.
>>> Surprisingly it seems to work fine. Could such hack be accepted as a
>>> patch to the plugin (if coded properly)? Is there a better place to 
>>> open the file?
>> The file should be opened in the hw_params callback (all PCM 
>> parameters are known in this time). Also, extending filename with PCM 
>> parameters should be optional (configurable). But the idea looks nice.
>>                         Jaroslav


please find enclosed a patch for the file plugin. The
checkpatch.pl script throws 5 bogus errors in doxygen comments.

Signed-off-by: Pavel Hofman <pavel.hofman at insite.cz>

* added support for including pcm stream params in the output filename
* added support for piping the stream to a shell command if the filename
string starts with a pipe char

Thanks a lot,


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