Takashi Sakamoto wrote:
On Aug 12 2014 16:09, Clemens Ladisch wrote:
Takashi Sakamoto wrote:
On Aug 11 2014 00:54, Clemens Ladisch wrote:
The old driver configured nothing but the rate. Is there any mechanism to set the stream format?
Yes. It's AV/C stream format information command. [...] But in this series of patches, I don't use this command. I expected the models to change stream format according to parameters in AMDTP packets such like the value of dbs field.
Apparently, the firmware doesn't support automatic format detection completely, and requires this command for the 2ch 32/44.1 kHz modes.
Apparently and completely, why? Please tell show reasons to judge about a lack of automatic format detection. When you developed and committed firewire-speakers driver, you confirmed all of combination for PCM rate/channels, didn't you?
When I wrote the driver, Jay tested which combinations did actually work (without any stream format information command; I don't have the spec), so that's what the driver ended up supporting: - 6ch at 32/44.1/48/96 kHz - 2ch at 48/96 kHz
If snd-oxfw also does not send the stream format information command, then I guess that 2ch at 32/44.1 kHz will not work either.
[...] Instead, we should consider the 2ch modes. This mode seems to be used for Dolby Pro Logic II and Dolby Digital but I don't know about the specification of Dolby something. If we drop these modes, the work to develop OXFW driver becomes simpler.
The driver does not need care about the format itself; the data is just sent as 16-bit words that pretend to be samples. All the driver has to do is to handle the "non-audio" bit in the "IEC958 Playback Default" or "IEC958 Playback PCM Stream" mixer controls; this can be added later.
Regards, Clemens