On Mon, Aug 25, 2014 at 10:52 PM, Jassi Brar <jassisinghbrar@xxxxxxxxx> wrote:
> On Mon, Aug 25, 2014 at 9:30 PM, Daniel Mack <zonque@xxxxxxxxx> wrote:
>> The UAC2 function driver currently responds to all packets at all times
>> with wMaxPacketSize packets. That results in way too fast audio
>> playback as the function driver (which is in fact supposed to define
>> the audio stream pace) delivers as fast as it can.
>>
>> Fix this by pre-calculating the size of each packet to meet the
>> requested sample rate and format. This won't be 100% accurate, but
>> that's acceptable.
>>
> For rates like 44100 we will always hear clicks because we can not
> transfer 176400bytes by packets of equal size over duration of 1
> second. The inaccuracy here is due to the way we program, and not due
> to system/bus load.
>
> Have you tried the approach I suggested - {4x176, 1x178} pattern
> packets, and does that not work? Please let me know if I am
> overlooking something. Otherwise let us do the best we can (If you
> want me to give that a try, I can in a day or two).
>
>> @@ -187,7 +189,7 @@ agdev_iso_complete(struct usb_ep *ep, struct usb_request *req)
>>
>> if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
>> src = prm->dma_area + prm->hw_ptr;
>> - req->actual = req->length;
>> + req->length = req->actual = uac2->c_pktsize;
>>
> This doesn't seem right.
> We asked req->length to be transmitted by the udc which shouldn't
> return until that is done. So at this point setting 'length' doesn't
> mean much. The original assignment to 'actual' is only because we want
> to ignore any issue that caused the udc to transmit fewer bytes (we
> drop that data).
>
> I believe you want to do the following in afunc_set_alt().
> - req->length = prm->max_psize;
> + req->length = uac2->c_pktsize;
>
Sorry I intended...
- prm->max_psize = hs_epin_desc.wMaxPacketSize;
+ prm->max_psize = agdev->uac2.c_pktsize;
Also USB-IN is capture for host, but in f_uac2 it is playback. So you
may want to do
- rate = opts->c_srate * opts->c_ssize * num_channels(opts->c_chmask);
- rate = opts->p_srate * opts->p_ssize * num_channels(opts->p_chmask);
BTW, why not do the same for USB-OUT as well? it shouldn't hurt.
Thanks
Jassi
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