[alsa-devel] [PATCH] crec: Add option to specify codec ID

[Vinod Koul]

On Fri, Nov 18, 2016 at 04:17:37PM +0000, Charles Keepax wrote:
> On Fri, Nov 18, 2016 at 08:39:38AM -0600, Pierre-Louis Bossart wrote:
> > 
> > >>If you're debugging you may not care about the file format, you're
> > >>actually interested in the raw data you get from the codec so dumping
> > >>the output to a raw file would be useful even if you can't load that
> > >>file into a music player.
> > >
> > >While I agree with you on this, am worried that adding codecs may make
> > >people think that we can record mp3 file for exmaple, which is not the case.
> > >
> > >I think we can add pcm and bespoke as formats supported and allow any format to
> > >be dumped to stdio. That way it is pretty clear to people ...
> > 
> > Crec as is it is pretty useless with PCM only...If we added the profile
> > selection and things like bitrate information it'd be straightforward to
> > support elementary bitstreams like MP3 or AAC ADTS, you just dump the data
> > to a file. Things that require a header or MP4 integration would require
> > additional libraries, this is no longer 'tiny'.
> 
> What about this as a suggestion, if we remove the code that adds
> the WAV header. Then all the output from crecord is raw data and
> the addition of any headers or additional wrapping is up to the
> user. That keeps crecord 'tiny' and allows us to support all the
> formats in a consistent way so no one gets confused.

Naah, crecord is a utility. If you need to do above you have tinycompress
APIs to get the data and pack it the way you like.. You don't and shouldn't
use crecord for that.

> We haven't actually used the WAV header stuff since the very
> early versions of our firmware that didn't use compression on the
> stream and actually did output PCM data and I don't think anyone
> else has ever used the compressed interface for PCM.

Thats fine by me. The only reason we have a WAV header is that we can pack
PCM files, for rest of the formats it become tricky as Pierre mention so lets
not go that road :)

-- 
~Vinod