On Fri, Aug 9, 2024 at 10:01 PM Jaroslav Kysela <perex@xxxxxxxx> wrote: > > On 09. 08. 24 14:52, Pierre-Louis Bossart wrote: > > >> And metadata > >> ioctl can be called many times which can meet the ratio modifier > >> requirement (ratio may be drift on the fly) > > > > Interesting, that's yet another way of handling the drift with userspace > > modifying the ratio dynamically. That's different to what I've seen before. > > Note that the "timing" is managed by the user space with this scheme. > > >> And compress API uses codec as the unit for capability query and > >> parameter setting, So I think need to define "SND_AUDIOCODEC_SRC' > >> and 'struct snd_dec_src', for the 'snd_dec_src' just defined output > >> format and output rate, channels definition just reuse the snd_codec.ch_in. > > > > The capability query is an interesting point as well, it's not clear how > > to expose to userspace what this specific implementation can do, while > > at the same time *requiring* userpace to update the ratio dynamically. > > For something like this to work, userspace needs to have pre-existing > > information on how the SRC works. > > Yes, it's about abstraction. The user space wants to push data, read data back > converted to the target rate and eventually modify the drift using a control > managing clocks using own way. We can eventually assume, that if this control > does not exist, the drift cannot be controlled. Also, nice thing is that the > control has min and max values (range), so driver can specify the drift range, > too. > > And again, look to "PCM Rate Shift 100000" control implementation in > sound/drivers/aloop.c. It would be nice to have the base offset for the > shift/drift/pitch value standardized. Thanks. But the ASRC driver I implemented is different, I just register one sound card, one device/subdevice. but the ASRC hardware support 4 instances together, so user can open the card device 4 times to create 4 instances then the controls can only bind with compress streams. I think I can remove the 'SNDRV_COMPRESS_SRC_RATIO_MOD', Only define a private type for driver, which means only the ASRC driver and its user application know the type. For the change in 'include/uapi/sound/compress_params.h", should I keep them, is there any other suggestion for them? Best regards Shengjiu Wang > > Jaroslav > > -- > Jaroslav Kysela <perex@xxxxxxxx> > Linux Sound Maintainer; ALSA Project; Red Hat, Inc. >
