ALSA AAF PCM: speaker-test reports "Write error: -32, Broken pipe" with -p option but works with -P option

[liuyq0509-ux]

Hi everyone,

I am testing an ALSA AAF PCM plugin for AVTP audio streaming on an ARM development board. The PCM configuration is as follows:

pcm.aaf0 {
type aaf
ifname eth0.5
addr 01:AA:AA:AA:AA:AA
prio 2
streamid AA:BB:CC:DD:EE:FF:000B
mtt 50000
time_uncertainty 1000
frames_per_pdu 12
ptime_tolerance 100
}

When I run speaker-test with the following command:

speaker-test -p 25000 -F S16_BE -c 2 -r 48000 -D aaf0

The device is opened successfully and the hardware parameters are set:
Playback device is aaf0
Stream parameters are 48000Hz, S16_BE, 2 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 1 to 206158430
Period size range from 0 to 206158431
Requested period time 25000 us
Periods = 4
was set period_size = 1200
was set buffer_size = 4800
0 - Front Left
Write error: -32, Broken pipe
Write error: -32, Broken pipe
Write error: -32, Broken pipe
...

However, if I change the command to use -P:

speaker-test -P 480 -F S16_BE -c 2 -r 48000 -D aaf0

The test runs normally without any Broken pipe errors:

layback device is aaf0
Stream parameters are 48000Hz, S16_BE, 2 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 1 to 206158430
Period size range from 0 to 206158431
Periods = 480
was set period_size = 12000
was set buffer_size = 5760000
0 - Front Left
1 - Front Right
Time per period = 0.283478
0 - Front Left
1 - Front Right
Time per period = 0.242246

Does anyone know why -p 25000 causes Broken pipe while -P 480 works?

Could this be related to:

• ALSA buffer/period configuration?
• AAF plugin internal scheduling?
• AVTP packet timing requirements?
• PTP synchronization?
• CBS/QoS configuration?

Any suggestions would be appreciated. Thanks!