From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [PATCH 1/1] pcm:file: delegate htimestamping to slave instead of always getting real_htimestamp Date: Tue, 28 Mar 2017 08:39:49 +0200 Message-ID: References: <1490269245-16858-1-git-send-email-sutar.mounesh@gmail.com> <7f32547e4f164dc8958b242129b8f9ad@SVR-IES-MBX-04.mgc.mentorg.com> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by alsa0.perex.cz (Postfix) with ESMTP id 3C4B9266A34 for ; Tue, 28 Mar 2017 08:39:50 +0200 (CEST) In-Reply-To: <7f32547e4f164dc8958b242129b8f9ad@SVR-IES-MBX-04.mgc.mentorg.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: "Sutar, Mounesh" Cc: "sutar.mounesh@gmail.com" , "alsa-devel@alsa-project.org" , Andreas Pape List-Id: alsa-devel@alsa-project.org On Tue, 28 Mar 2017 08:37:24 +0200, Sutar, Mounesh wrote: > > ping No need for ping. Please give some time for review. Takashi > > -----Original Message----- > From: sutar.mounesh@gmail.com [mailto:sutar.mounesh@gmail.com] > Sent: 23 March 2017 17:11 > To: patch@alsa-project.org > Cc: alsa-devel@alsa-project.org; Sutar, Mounesh ; Andreas Pape ; Mounesh Sutar > Subject: [PATCH 1/1] pcm:file: delegate htimestamping to slave instead of always getting real_htimestamp > > From: Andreas Pape > > purpose of this fix, is to read most accurate timestamps. > > From documentation of /src/pcm/pcm.c, we can see: > """" \par Timestamp mode > > The timestamp mode specifies, if timestamps are activated. Currently, only #SND_PCM_TSTAMP_NONE and #SND_PCM_TSTAMP_MMAP modes are known. > The mmap mode means that timestamp is taken on every period time boundary. Corresponding position in the ring buffer assigned to timestamp can be obtained using #snd_pcm_htimestamp() function. """" > > As snd_pcm_generic_htimestamp() internally calls snd_pcm_htimestamp() to read time, so accurate timestamp can be read from snd_pcm_generic_htimestamp(). > > Also, in case of pcm_file, if the underlying slave is hardware, then we would wish to read elapsed hardware time, as it will be the most accurate, as opposed to the elapsed wall time. > This will provide pcm_file with the most accurate timestamps. > > Following are the timesamps read with timestamp enabled, for with fix and without fix scenarios: > > 1> With fix: > :~#time aplay --enable-tstamp -Dhtstamp_test --period-time=5000 -v -fdat /dev/urandom Playing raw data '/dev/urandom' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo File PCM (file=/tmp/swarate_out.wav) Final file PCM (file=/tmp/swarate_out.wav) .. > > Slave: Hardware PCM card 0 'imx6q-sabresd-wm8962' device 0 subdevice 0 Its setup is: > stream : PLAYBACK > access : RW_INTERLEAVED > format : S16_LE > subformat : STD > channels : 2 > rate : 48000 > exact rate : 48000 (48000/1) > msbits : 16 > buffer_size : 24000 > period_size : 240 > period_time : 5000 > tstamp_mode : ENABLE > . > . > Before sleep = 142:409.807623 > After sleep = 142:409.807623 > Before sleep = 142:414.806016 (calling snd_pcm_htimestamp(handle, &avail, &tstamp_before)) sleep of 2 milisec After sleep = 142:414.806016 (calling snd_pcm_htimestamp(handle, &avail, &tstamp_after) From the above timestamps, we can see that slave has returned the same timestamps, as --period-time choosen is 5msec. > > 2> Without this fix: > The timestamps are returned with realtime value. > > :~# time aplay --enable-tstamp -Dhtstamp_test --period-time=5000 -v -fdat /dev/urandom Playing raw data '/dev/urandom' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo File PCM (file=/tmp/swarate_out.wav) Final file PCM (file=/tmp/swarate_out.wav) . > . > Slave: Hardware PCM card 0 'imx6q-sabresd-wm8962' device 0 subdevice 0 Its setup is: > stream : PLAYBACK > access : RW_INTERLEAVED > format : S16_LE > subformat : STD > channels : 2 > rate : 48000 > exact rate : 48000 (48000/1) > msbits : 16 > buffer_size : 24000 > period_size : 240 > period_time : 5000 > tstamp_mode : ENABLE > . > . > Before sleep = 241:136.875845 (calling snd_pcm_htimestamp(handle, &avail, &tstamp_before)) sleep of 2 milisec After sleep = 241:139.076376 (calling snd_pcm_htimestamp(handle, &avail, &tstamp_after) > > We can observe here, the timestamps shows time diff of ~2ms, which is the time gap of sleep duration. > Before sleep = 241:139.617588 > After sleep = 241:141.746845 > Before sleep = 241:142.291618 > After sleep = 241:144.406406 > Before sleep = 241:144.951421 > After sleep = 241:147.066118 > Before sleep = 241:147.623421 > After sleep = 241:149.740573 > > Signed-off-by: Andreas Pape > Signed-off-by: Mounesh Sutar > > diff --git a/src/pcm/pcm_file.c b/src/pcm/pcm_file.c index 8012251..fe36a1c 100644 > --- a/src/pcm/pcm_file.c > +++ b/src/pcm/pcm_file.c > @@ -728,7 +728,7 @@ static const snd_pcm_fast_ops_t snd_pcm_file_fast_ops = { > .poll_descriptors_count = snd_pcm_generic_poll_descriptors_count, > .poll_descriptors = snd_pcm_generic_poll_descriptors, > .poll_revents = snd_pcm_generic_poll_revents, > - .htimestamp = snd_pcm_generic_real_htimestamp, > + .htimestamp = snd_pcm_generic_htimestamp, > }; > > /** > -- > 2.7.4 >