Thanks a lot. That helps. >-----Original Message----- >From: Giuliano Pochini [mailto:pochini@xxxxxxxx] >Sent: Saturday, April 25, 2009 5:50 PM >To: Harsha, Priya >Cc: alsa-devel@xxxxxxxxxxxxxxxx >Subject: Re: .pointer return value > >On Thu, 23 Apr 2009 19:34:08 +0530 >"Harsha, Priya" <priya.harsha@xxxxxxxxx> wrote: > >> Can anyone educate me on what value should be returned to .pointer function? >> Should I be passing the number of frames played till that point from the time stream started or >thnumber of frames played such that the bytes is within the buf_size? > >The latter: it's the index of the last transferred frame in the ring buffer. > > >> And if I am using, snd_pcm_indirect_playback_pointer, what should be my input to it? >> Should I be passing the number of bytes played till that point from the time stream started or the >number of bytes within buf_size? > >In practice, they're both fine. After a quick look at the sources >in /include/sound/pcm-indirect.h: > >---- >static inline snd_pcm_uframes_t >snd_pcm_indirect_playback_pointer(struct snd_pcm_substream *substream, > struct snd_pcm_indirect *rec, unsigned int ptr) { > int bytes = ptr - rec->hw_io; > if (bytes < 0) > bytes += rec->hw_buffer_size; > rec->hw_io = ptr; >---- > >It cares about the difference from the last position to the current one and >it adds hw_buffer_size if ptr wrapped around. > >Side note: >I can guess it may not behave correctly in case of long latencies when >bytes < -hw_buffer_size. Perhaps should the "if" be changed to "while" ? > > > >-- >Giuliano. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
