| Message ID | 20240507083142.557299-1-perex@perex.cz (mailing list archive) |
|---|---|
| Headers | show |
| Series | ALSA: pcm: reinvent the stream synchronization ID API | expand |
On Tue, 07 May 2024 10:26:17 +0200, Jaroslav Kysela wrote: > > Until the commit e11f0f90a626 ("ALSA: pcm: remove SNDRV_PCM_IOCTL1_INFO > internal command"), there was a possibility to pass information > about the synchronized streams to the user space. The mentioned > commit removed blindly the appropriate code with an irrelevant comment. > > The revert may be appropriate, but since this API was lost for several > years without any complains, it's time to improve it. The hardware > parameters may change the used stream clock source (e.g. USB hardware) > so move this synchronization ID to hw_params as read-only field. > > It seems that pipewire can benefit from this API (disable adaptive > resampling for perfectly synchronized PCM streams) now. I find the idea is fine. But as Sakamoto-san suggested in the previous thread, it's no urgent issue, and I'm inclined to postpone the merge after 6.10 merge window. So let's brew the stuff well for now. thanks, Takashi
Until the commit e11f0f90a626 ("ALSA: pcm: remove SNDRV_PCM_IOCTL1_INFO internal command"), there was a possibility to pass information about the synchronized streams to the user space. The mentioned commit removed blindly the appropriate code with an irrelevant comment. The revert may be appropriate, but since this API was lost for several years without any complains, it's time to improve it. The hardware parameters may change the used stream clock source (e.g. USB hardware) so move this synchronization ID to hw_params as read-only field. It seems that pipewire can benefit from this API (disable adaptive resampling for perfectly synchronized PCM streams) now. v2->v3: - fix pcm_sync_empty() function (wrong comparison) [thanks Takashi Sakamoto] - more documentation for snd_pcm_set_sync_per_card (ID composition) v1->v2: - remove union usage per Takashi's request - reduce memory usage - use standard ID generation scheme Jaroslav Kysela (2): ALSA: pcm: reinvent the stream synchronization ID API ALSA: pcm: optimize and clarify stream sychronization ID API include/sound/pcm.h | 19 ++++++++++++-- include/uapi/sound/asound.h | 13 +++------- sound/core/pcm_lib.c | 50 +++++++++++++++++++++++++++++-------- sound/core/pcm_native.c | 6 +++++ sound/pci/emu10k1/p16v.c | 17 +++++++++---- 5 files changed, 79 insertions(+), 26 deletions(-)