[alsa-devel] [PATCH v3 1/3] ASoC: davinci-mcasp: Constraint on the period and buffer size based on FIFO usage

[Peter Ujfalusi]

On 03/18/2014 03:23 PM, Peter Ujfalusi wrote:
> On 03/18/2014 03:20 PM, Peter Ujfalusi wrote:
>> We need to place constraint on the period if the read or write AFIFO
>> is enabled and it is configured for more than one word otherwise
>> the DMA will fail in buffer configuration where the sizes are not
>> aligned with the requested FIFO configuration.
> 
> Oh, I edited the commit message and removed the text related to buffer size
> but I failed to do that for the commit title :(

Actually I still have issue with the constraint.
If I play a 48KHz sample with mplayer it is fine:
Trying preferred audio driver 'alsa', options '[none]'
alsa-init: requested format: 48000 Hz, 2 channels, 9
alsa-init: using ALSA 1.0.27.2
alsa-init: setup for 1/2 channel(s)
alsa-init: using device default
alsa-init: opening device in blocking mode
alsa-init: device reopened in blocking mode
alsa-init: got buffersize=96000
alsa-init: got period size 1600
alsa: 48000 Hz/2 channels/4 bpf/96000 bytes buffer/Signed 16 bit Little Endian
AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample)
AO: Description: ALSA-0.9.x-1.x audio output
AO: Author: Alex Beregszaszi, Zsolt Barat <joy at streamminister.de>
AO: Comment: under development
Building audio filter chain for 48000Hz/2ch/s16le -> 48000Hz/2ch/s16le...


However if I play 44.1KHz sample with mplayer:
Trying preferred audio driver 'alsa', options '[none]'
alsa-init: requested format: 44100 Hz, 2 channels, 9
alsa-init: using ALSA 1.0.27.2
alsa-init: setup for 1/2 channel(s)
alsa-init: using device default
alsa-init: opening device in blocking mode
alsa-init: device reopened in blocking mode
ALSA ERROR hw_params: set_near (BUFFER_TIME)
           value = 500000 : Invalid argument
ACCESS:  RW_INTERLEAVED
FORMAT:  S16_LE
SUBFORMAT:  STD
SAMPLE_BITS: 16
FRAME_BITS: 32
CHANNELS: 2
RATE: 44100
PERIOD_TIME: 50000
PERIOD_SIZE: NONE
PERIOD_BYTES: [4736 65536]
PERIODS: (1 19)
BUFFER_TIME: 500000
BUFFER_SIZE: 22050
BUFFER_BYTES: 88200
TICK_TIME: ALL
[AO_ALSA] Unable to set buffer time near: Invalid argument
Failed to initialize audio driver 'alsa'


Now if I place the same constraint to the buffer size as well and playing the
same 44.1KHz sample:
Trying preferred audio driver 'alsa', options '[none]'
alsa-init: requested format: 44100 Hz, 2 channels, 9
alsa-init: using ALSA 1.0.27.2
alsa-init: setup for 1/2 channel(s)
alsa-init: using device default
alsa-init: opening device in blocking mode
alsa-init: device reopened in blocking mode
alsa-init: got buffersize=88192
alsa-init: got period size 1696
alsa: 44100 Hz/2 channels/4 bpf/88192 bytes buffer/Signed 16 bit Little Endian
AO: [alsa] 44100Hz 2ch s16le (2 bytes per sample)
AO: Description: ALSA-0.9.x-1.x audio output
AO: Author: Alex Beregszaszi, Zsolt Barat <joy at streamminister.de>
AO: Comment: under development
Building audio filter chain for 44100Hz/2ch/s16le -> 44100Hz/2ch/s16le...

It seams that I need to place the same constraint step to both period size and
buffer size.
For some reason snd_pcm_hw_params_set_buffer_time_near() fails in case of
44.1KHz when asking for 0.5s buffer when I placed step 32 constraint to period
size. Placing the same 32 steps constraint to the buffer size as well will
make things working (for mplayer at least)

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