[alsa-devel] Application supporting forward/rewind APIs

[Anuj Aggarwal]

Yeah, I am looking for some sample application to test forward/rewind
functionality.

Regards,
Anuj

On Thu, Sep 24, 2009 at 1:27 PM, Raymond Yau
<superquad.vortex2 at gmail.com> wrote:
> Do you mean that there is no test program to verify the implementation is
> correct ?
>
> Some sound card 's hardware has FIFO buffer.
>
> For example , au88x0
>
> according to patent 6167465
>
> Additionally, a first-in-first-out (FIFO) buffer is established for the DMA
> channel. Then a DMA request is generated in order to begin filling the FIFO
> buffer with data from the first data segment 150(0) using the information
> provided by CPU 210.
>
>
> The FIFO buffer may be any suitable size capable of handling bus latencies
> while small enough such that the memory requirement is not overly
> burdensome. In one embodiment of the present invention, the FIFO buffer is
> 32 samples or words in depth, which would withstand a maximum bus latency of
> about 4 microseconds. By way of example, if 48 DMA channels trigger
> simultaneously, with a trigger level set at half the buffer size (16
> samples), each DMA channel can wait 16 samples (20 microseconds per sample),
> or approximately 320 microseconds before running out of data.
>
>
> It seem that alsa-lib should not allow application to rewind the application
> pointer to hardware pointer since you cannot write the next sample because
> of FIFO buffer even using mmap read/write
>
> or bug in *snd_pcm_rewindable() ?*
>
>
> 2009/9/24 Takashi Iwai <tiwai at suse.de>
>
>> At Thu, 24 Sep 2009 13:04:24 +0530,
>> Anuj Aggarwal wrote:
>> >
>> > Hi,
>> >
>> > I want to try the forward/rewind APIs supported by the ALSA library.
>> > Can someone point to an ALSA application which exercises these APIs?
>>
>> Pulseaudio is using snd_pcm_rewind().
>> About snd_pcm_forward(), I don't know of...
>>
>>
>> Takashi
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-- 
Best Regards,
Anuj Aggarwal