missing sound on kernel-5.15
chihhao chen
chihhao.chen at mediatek.com
Mon Aug 22 10:06:58 CEST 2022
I am testing many headsets on Android platform with different kernel
versions.
On kernel-5.10, calling sequence for playback is
1. snd_usb_hw_params -> set highest sampling rate, no
SAMPLING_FREQ_CONTROL USB request sent in this stage
2. snd_pcm_release
3. snd_usb_hw_params -> set proper sampling rate, still no
SAMPLING_FREQ_CONTROL USB request
4. snd_usb_pcm_parepare -> in configure_endpoint SAMPLING_FREQ_CONTROL
USB request was sent on USB bus
With the same calling sequence, a slightly behavior change on kernel-
5.15 is
1. snd_usb_hw_params -> set highest sampling rate,
SAMPLING_FREQ_CONTROL USB request was sent on USB bus
2. snd_pcm_release
3. snd_usb_hw_params -> set proper sampling rate, SAMPLING_FREQ_CONTROL
USB request was sent too
(because configure_endpoint was moved to snd_usb_hw_params function)
4. snd_usb_pcm_parepare -> no SAMPLING_FREQ_CONTROL USB
request because of USB EP flag check
I checked all USB packets and confirmed audio data output was correct.
But there may be missing sound problem for the first sound with many
headsets (for example Samsung headset).
I found this issue is related to two-times sampling rate set request.
(I tried to forcibly skip first USB request, everything became okay.)
So do you guys know why configure_endpoint was moved to
snd_usb_hw_params?
Or could you provide patch for this problem?
Many thanks
Chihhao
More information about the Alsa-devel
mailing list