Messages in this thread | | | Date | Tue, 28 Oct 2014 15:05:16 +0000 | From | Qais Yousef <> | Subject | Re: [PATCH 00/11] Add AXD Audio Processing IP driver |
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On 10/28/2014 02:13 PM, Greg Kroah-Hartman wrote: > On Tue, Oct 28, 2014 at 01:18:28PM +0000, Qais Yousef wrote: >> On 10/28/2014 11:55 AM, Clemens Ladisch wrote: >>> Qais Yousef wrote: >>>> AXD Audio Processing IP performs audio decoding, encoding, mixing, equalisation, >>>> synchronisation and playback. >>> What exactly do you mean with "synchronisation" and "playback"? >> Synchronisation refers to accurate audio playout relative to a master >> clock source including compensation of drift between the master clock >> source and the playout clock of the audio hardware. Hence allowing >> synchronised audio playout across multiple independent devices. >> >> Playback simple refers to the fact that AXD is capable of managing audio >> playout hardware like I2S and SPDIF interfaces. >> >> >>>> It doesn't fit in alsa subsystem but I Cced them to confirm. >>> ... because those two words sound like something that a sound card could do. >> The problem mainly stems from the fact that we take a variety of >> compressed audio as input and we could perform audio encoding. The >> problem with the compressed audio is that the range of decoders and >> configuration supported in alsa is limited and there's no support for >> taking raw pcm and producing compressed output. I'm not an expert on >> alsa but when I looked it looked like there's more infra structure >> required. >> >> The following not supported points from Documentation/sound/alsa/compress_offload.txt affect us: >> >> - Volume control/routing is not handled by this API. Devices exposing a >> compressed data interface will be considered as regular ALSA devices; >> volume changes and routing information will be provided with regular >> ALSA kcontrols. >> >> - Embedded audio effects. Such effects should be enabled in the same >> manner, no matter if the input was PCM or compressed. >> >> - Encoding/decoding acceleration is not supported as mentioned >> above. It is possible to route the output of a decoder to a capture >> stream, or even implement transcoding capabilities. This routing >> would be enabled with ALSA kcontrols. > So instead you created a one-off api just for this hardware? Ick, no, > please work with the audio developers to incorporate it into the > standard Linux audio apis so that everyone can benifit and not require > special userspace programs to drive this hardware. > > thanks, > > greg k-h
OK. I'll wait to hear from alsa developers to see the extent of work required. I can't see it being trivial though. Would it be possible for this to be accepted into staging until this is resolved?
Thanks, Qais
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