[alsa-devel] [tinycompress]how should I call compress_open for aac ltp file playback?

Keyon.Jey yang.jie at linux.intel.com
Fri Jun 7 08:46:08 CEST 2013

On 06/07/2013 08:23 AM, Vinod Koul wrote:
> On Wed, Jun 05, 2013 at 04:27:44PM +0800, Keyon.Jey wrote:
>> On 06/05/2013 04:01 PM, Charles Keepax wrote:
>>> On Wed, Jun 05, 2013 at 02:46:04PM +0800, Keyon.Jey wrote:
>>>> I am trying to use tinycompress for hwdecoder. everything works fine,
>>>> but after compress_open (with profile = SND_AUDIOPROFILE_AAC level=0
>>>> ch_mode=0 rate_control=0), the playback of my aac-ltp-16bit-48KHz-Stereo
>>>> file is faster than it should be.  Am I wrong?
>>> Vinod is probably the person for this one, as I am not so
>>> familiar with what you guys have done internally. However, my
>>> guess would be you are not setting the sample_rate correctly? It
>>> likely needs to be set to the appropriate SNDRV_PCM_RATE_XXXX
>>> define. The source for cplay included in the tinycompress
>>> repository is a good example of using the tinycompress library.
>> thanks, Charles. the print log showed me that I have set
>> SNDRV_PCM_RATE_48000 which seems no problem.
>> the cplay example code is only for mp3 file, and it also not set
>> .level, .ch_mode and .rate_control.
>> Vinod, what's your suggestion?
> You need to ask your firmware guys, what are they expecting the these fields.
> Some decoder implementations can be different. But i would expect the audio to
> be broken, bad quality if that is the case.
> But the speed of playback can be due to different decoder output rate and
> different sampling rate configured. You are telling decoder 48Khz as CPM sample
> rate, is that what decoder is understanding and conversion to decoder values
> correct. Then you should check if the rendering to DAC is at 48KHz or not.
> --
> ~Vinod
thanks, Vinod, I will check with the firmware guys for these detail fields.


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