Hi, does anybody have any thoughts on my email below? The rate conversion code looks stable and untouched for a while. Thanks On Sun, 1 Aug 2010, Mark Hills wrote: > I have a device (snd-usb-caiaq) whose native sample format is S24_3BE. > When sample rate conversion is used, the audio becomes near silent, > distorted, and only in the left channel. > > It is reproducable with aplay (see example below). Recording is not > affected. Playback is correct if only format conversion is used. > > It looks something is causing the incorrect put function to be used by the > rate conversion. > > I traced it to linear_expand() and others, alsa-lib-src/pcm_rate_linear.c. > > Forcing the function to put S16 format into the destination buffer allows, > suprisingly, the sound to be heard correctly and at full volume from both > aplay and xwax: > > if (rate->put_idx == 10) > rate->put_idx = 6 > > I suspected that linear_init() is looking in the wrong place to choose the > attributes for the rate conversion. After some time spent I cannot see it. > > But is there any reason that the output buffer for the rate conversion > would not be in S24_3BE? And for the rate conversion to be misinformed? > > $ uname -s -r -v -p -i -m > Linux 2.6.34.1-mh #83 SMP PREEMPT Wed Jul 21 23:25:33 BST 2010 i686 pentium4 i386 > > $ alsacap > Card 0, ID `Audio8DJ', name `Audio 8 DJ' > Device 0, ID `Audio 8 DJ', name `Audio 8 DJ', 4 subdevices (4 available) > 2 channels, sampling rate 44100..96000 Hz > Sample formats: S24_3BE > Subdevice 0, name `subdevice #0' > Subdevice 1, name `subdevice #1' > Subdevice 2, name `subdevice #2' > Subdevice 3, name `subdevice #3' > > $ aplay -v -D plughw:Audio8DJ,0,0 halcyon-24000.wav > Playing WAVE 'halcyon-24000.wav' : Signed 16 bit Little Endian, Rate 24000 Hz, Stereo > Plug PCM: Rate conversion PCM (48000, sformat=S24_3BE) > Converter: linear-interpolation > Protocol version: 10002 > Its setup is: > stream : PLAYBACK > access : RW_INTERLEAVED > format : S16_LE > subformat : STD > channels : 2 > rate : 24000 > exact rate : 24000 (24000/1) > msbits : 16 > buffer_size : 10922 > period_size : 2730 > period_time : 113770 > tstamp_mode : NONE > period_step : 1 > avail_min : 2730 > period_event : 0 > start_threshold : 10922 > stop_threshold : 10922 > silence_threshold: 0 > silence_size : 0 > boundary : 715784192 > Slave: Hardware PCM card 0 'Audio 8 DJ' device 0 subdevice 0 > Its setup is: > stream : PLAYBACK > access : MMAP_INTERLEAVED > format : S24_3BE > subformat : STD > channels : 2 > rate : 48000 > exact rate : 48000 (48000/1) > msbits : 24 > buffer_size : 21845 > period_size : 5461 > period_time : 113770 > tstamp_mode : NONE > period_step : 1 > avail_min : 5461 > period_event : 0 > start_threshold : 21844 > stop_threshold : 21845 > silence_threshold: 0 > silence_size : 0 > boundary : 1431633920 > appl_ptr : 0 > hw_ptr : 0 > > -- Mark _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
