On 12. 08. 24 12:24, Shengjiu Wang wrote:
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.
It's just a reason to add the subdevice code for the compress offload layer
like we have in other APIs for overall consistency. I'll try to work on this.
I think I can remove the 'SNDRV_COMPRESS_SRC_RATIO_MOD',
Yes.
Only define a private type for driver, which means only the ASRC driver
and its user application know the type.
The control API should be used for this IMHO.
For the change in 'include/uapi/sound/compress_params.h", should I
keep them, is there any other suggestion for them?
I don't see a problem there.
Jaroslav
--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
