[alsa-devel] Fwd: ALSA queries
Takashi Iwai
tiwai at suse.de
Mon Aug 6 14:51:50 CEST 2018
On Mon, 06 Aug 2018 14:29:26 +0200,
Chakravarthi Pradeep wrote:
>
> Hello Takashi,
>
> Thanks for your explanation about period and periods.
>
> > Erm, I'm no consultant. Does your driver issue really
> > snd_pcm_period_elapsed() or not? You should know that.
> >
> > If the problem happens even if the driver really calls
> > snd_pcm_period_elapsed(), then it's another cause
>
> I'm calling snd_pcm_period_elapsed() in my audio thread
> snd_pcm_period_elapsed(drv->substream);
> I'm calling this <snd_pcm_period_elapsed()> function after one frame
> is copied to from PCIe device. However, hwptr is not updated and no
> sound in the VLC application.
OK, so you are sure that the function is really called, not only in
theory, right? Then the next item to check is the pointer callback.
The hwptr is updated based on the value returned from this callback.
Takashi
>
> Regards,
> Chakravarthi Pradeep K
> On Mon, Aug 6, 2018 at 2:09 PM Takashi Iwai <tiwai at suse.de> wrote:
> >
> > On Sun, 05 Aug 2018 20:09:47 +0200,
> > Chakravarthi Pradeep wrote:
> > >
> > > ---------- Forwarded message ---------
> > > From: Chakravarthi Pradeep <doubleq7 at gmail.com>
> > > Date: Sun 5 Aug, 2018, 14:19
> > > Subject: Re: [alsa-devel] ALSA queries
> > > To: <tiwai at suse.de>
> > >
> > >
> > > Hello Takashi,
> > >
> > > Thanks for your reply.
> > >
> > > periods_min = the minimal number of periods
> > > period_bytes_min = the minimal size of bytes for one period
> > > period_bytes_max = the maximal size of bytes for one period
> > >
> > >
> > > periods_min = the minimal number of periods : what is meaning of
> > > periods , is it minimal number of interrupts ?
> >
> > The "period" in ALSA PCM definition represents the interval time (or
> > frames) of the periodical interrupts on the ring buffer. If the irq
> > is issued for each 256 frames while the ring buffer size is 1024
> > frames, periods = 1024/256 = 4. The periods_min defines the minimal
> > number of periods the hardware may accept.
> >
> > > period_bytes_min = the minimal size of bytes for one period : it
> > > means, minimal size of bytes per interrupt in case of device, Is it
> > > correct ?
> >
> > Correct.
> >
> > > what about period_max ?
> >
> > The maximal number of periods, the counter-part of periods_min.
> >
> >
> > > It's most likely the ALSA PCM core's safety stop; your driver seem to
> > > have missed snd_pcm_period_elapsed() calls, so the hwptr isn't
> > > updated, resulting in XRUN. ALSA PCM core checks such XRUN condition
> > > with the own timer.
> > >
> > > I'm attaching my driver thread along with this mail. Can you please
> > > let me know if I have missed something in audio thread. ?. How to make
> > > sure in driver that, trigger stop should be called only when stop
> > > command is sent from application.
> >
> > Erm, I'm no consultant. Does your driver issue really
> > snd_pcm_period_elapsed() or not? You should know that.
> >
> > If the problem happens even if the driver really calls
> > snd_pcm_period_elapsed(), then it's another cause.
> >
> > > I'm getting cut cut cut ... noise along with audio in VLC application.
> > > Initially for 2 or 4 seconds, cut cut cut noise is not heard in VLC
> > > application, However after almost after 5 sec ,I can hear cut cut cut
> > > noise in VLC application. With my analysis, hwptr is getting updated
> > > properly however I have doubt in app_ptr. I'm attaching the excl sheet
> > > with hw_ptr,app_ptr and buf_pos values.
> >
> > Do the buffer size and period size are set really as expected?
> > Often the driver misses the fact that PCM core doesn't guarantee the
> > alignment of buffer size and period size unless specified explicitly
> > via hw constraints. That is, as default, it's possible to set a
> > buffer size 3000 bytes for the period size 64 bytes. Then the last
> > period is partial.
> >
> > For aligning the period and the buffer sizes, call
> > snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
> > in the open callback.
> >
> >
> > Takashi
> >
> > >
> > > How to remove the cut cut cut ... noise in audio ?
> > >
> > > Regards,
> > > Chakravarthi
> > >
> > > On Fri, Aug 3, 2018 at 1:05 PM Takashi Iwai <tiwai at suse.de> wrote:
> > > >
> > > > On Thu, 02 Aug 2018 16:31:13 +0200,
> > > > Chakravarthi Pradeep wrote:
> > > > >
> > > > > I'm working on ALSA driver for PCIe card. My ALSA driver and it's
> > > > > initializing struct snd_pcm_hardware with below parameter.
> > > > >
> > > > > /************************ code start
> > > > > ************************************************/
> > > > > static struct snd_pcm_hardware audio_pcm_hardware = {
> > > > > .info = (SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_MMAP |
> > > > > SNDRV_PCM_INFO_MMAP_VALID |
> > > > > SNDRV_PCM_INFO_BLOCK_TRANSFER |
> > > > > SNDRV_PCM_INFO_RESUME ),
> > > > > .formats = (SNDRV_PCM_FORMAT_S16_LE | SNDRV_PCM_FORMAT_S24_LE),
> > > > > .rates = (SNDRV_PCM_RATE_44100 | SNDRV_PCM_RATE_48000 |
> > > > > SNDRV_PCM_RATE_96000 | SNDRV_PCM_RATE_192000),
> > > > > .rate_min = 44100,
> > > > > .rate_max = 192000,
> > > > > .channels_min = 2,
> > > > > .channels_max = 8,
> > > > > .buffer_bytes_max = 76800, /*75 kbytes */
> > > > > .period_bytes_min = 512,//4410, /* (channel (2) * sample_rate (44100)
> > > > > * bit width (24)) / (60 * 8) */
> > > > > .period_bytes_max = 16*1024,
> > > > > .periods_min = 10,
> > > > > .periods_max = 255,
> > > > >
> > > > > };
> > > > > /************************ code end
> > > > > ************************************************/
> > > > >
> > > > > 1) I did not understand what is significance of periods_min ,
> > > > > period_bytes_min , period_bytes_max and periods_max. Can you please
> > > > > tell me what is importance of these parameter and what value should be
> > > > > mentioned according into ALSA.
> > > >
> > > > These three defines the values your hardware may accept:
> > > > periods_min = the minimal number of periods
> > > > period_bytes_min = the minimal size of bytes for one period
> > > > period_bytes_max = the maximal size of bytes for one period
> > > >
> > > > > 2) snd_pcm_ops trigger callback is getting called in the driver when
> > > > > application sends "start" command. But ALSA driver is stopping by
> > > > > itself after one frame is copied to ALSA framework, without waiting
> > > > > for "stop" command.
> > > > >
> > > > > For instance:
> > > > > In trigger callback , I'm getting these logs after one frame is copied.
> > > > > Trigger:Start (When Play button is selected/clicked in application,
> > > > > Start command is sent to ALSA driver)
> > > > > Dma transfer is completed.
> > > > > Trigger:Stop. (When Stop button is selected/clicked in application,
> > > > > Stop command is sent to ALSA driver. But stop button is not clicked in
> > > > > this case)
> > > >
> > > > It's most likely the ALSA PCM core's safety stop; your driver seem to
> > > > have missed snd_pcm_period_elapsed() calls, so the hwptr isn't
> > > > updated, resulting in XRUN. ALSA PCM core checks such XRUN condition
> > > > with the own timer.
> > > >
> > > >
> > > > Takashi
> > >
> > >
> > >
> > > --
> > > Thanks and Regards
> > > Chakravarthi Pradeep.K
> > > Ph: 91 9980434900
> > > [1.2 <text/html; UTF-8 (quoted-printable)>]
> > >
> > > static int uhdc_audio_thread(void *data)
> > > {
> > > char *audio_frame = NULL;
> > > int count = 0;
> > > uhdc_t3_card_driver *drv = (uhdc_t3_card_driver *)data;
> > > struct snd_pcm_runtime *runtime = drv->substream->runtime;
> > >
> > >
> > > audio_frame = kmalloc(MAX_AUDIO_SIZE, GFP_DMA);
> > > if(!audio_frame)
> > > {
> > > return -ENOMEM;
> > > }
> > > while(1)
> > > {
> > >
> > > if (kthread_should_stop())
> > > {
> > > dbg_alsa( "###### %s %d\n",__FUNCTION__,__LINE__);
> > > break;
> > > }
> > > dbg_alsa( "###### Waiting for audio signal %s_%d\n",__FUNCTION__,__LINE__);
> > > wait_event_interruptible (audio_interrupt, (atomic_read (&audio_data_ready)));
> > > atomic_set (&audio_data_ready, 0);
> > > g_count = get_audio_size(g_temp_lro);
> > > count = g_count;
> > > printk( "######audio signal received and audio size:%d runtime->period_size:%d %s_%d\n",g_count,runtime->period_size,__func__,__LINE__);
> > >
> > > /* dma read is done here */
> > > /* audio_frame contains audio data */
> > > memcpy(drv->substream->runtime->dma_area + drv->buf_pos ,audio_frame,count);
> > >
> > > /* update the buf_pos */
> > > // here the (auto)increase of buf_pos is handled
> > > drv->buf_pos += count;
> > > drv->buf_pos %= drv->pcm_buffer_size;
> > >
> > >
> > > printk("\n\n\n hwptr=%d appl=%d pos=%d\n",
> > > (int)frames_to_bytes(runtime,runtime->status->hw_ptr),(int)frames_to_bytes(runtime, runtime->control->appl_ptr),drv->buf_pos);
> > > /* Below line needs to be uncommented for pointer to be updated in the alsa lib */
> > > snd_pcm_period_elapsed(drv->substream);
> > >
> > > try_to_freeze();
> > >
> > > }
> > >
> > > kfree(audio_frame);
> > > audio_frame = NULL;
> > >
> > > return 0 ;
> > >
> > > }
> > > [3 hwptr_app_ptr_buf_pos_analysis.xlsx <application/vnd.openxmlformats-officedocument.spreadsheetml.sheet (base64)>]
> > >
>
>
>
> --
> Thanks and Regards
> Chakravarthi Pradeep.K
> Ph: 91 9980434900
>
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