Bit for bit from harddrive to soundcard

[zman9001]

Hi, I realize that this isnt a bug but, to me, it is a big deal. I've been souring forums and bug trackers and blogs but I just can't seem to find an answer to my dillemma! All I want to do is get a soundfile sampled at 96kHz from my harddrive through an audio player, through pulse, through alsa and into my soundcard's DAC without any downsampling. Please tell me this is possible. I don't give a hoot about system sounds or mixing streams or upsampling overhead. I just want my soundcard to see 96kHz. Also, I'm not sure which component to place this ticket in as I've come to the conclusion that it applies to them all :) so bear with me please.

Any and all help is GREATLY appreciated, Thank you all very much in advance, Rob

[coling]

To be honest you'd probably be better joining the mailing list and asking there. It's a more appropriate channel for discussing and support like that, where as Trac is really more of a bug tracker.

It would also help to know what you have tried etc.

To start you off, what would happen if you set:

default-sample-rate = 96000

in /etc/pulse/daemon.conf?

Have you tried that?

It will mean that everything gets resampled to 96000, which in turn means that your system may be under increased load when playing simple things like desktop effects etc.

It will be interesting to see whether Lennart's work on module-alsa-card support will allow to switch the frequency as part of the profile switching.... (even if it doesn't now I'd imagine it will do in the future).

[zman9001]

Thanks you for your reply. I wasn't aware that a mailing list could be of use in these matters I was rather looking for a pulseaudio forum (which i didnt find).

Anyway, I have in fact set the default-sample-rate parameter to 96000 and am using speex-float-5 to resample other rates. I suspect that this is working as it should because pulseaudio uses about 11-15% processor when I'm playing back 44.1 and 48 kHz files as compared to about 3% when playing 96 kHz files. In any case I don't have a problem with saying goodbye to system sound effects if it becomes an issue. My concern was whether alsa was messing with the signal in any way before it reaches the soundcard. I don't think it is because I would notice processor load somewhere but I don't know anything about the intrinsics of software sound transfer, which is why I came here for a word of advice.

Also, what's this about module-alsa-card support and profile switching? I'm not sure what you mean by that. I suppose I'll look into it now.

Thanks again for your reply, Rob

[coling]

Hi zman,

Yeah, no forums just a mailing list. All forums are are a frontend to mailing lists anyway so there is very little point in having both. Just use gmane.org to add the mailing list to your favourite news reader (e.g. thunderbird) and off you go.

Yeah, if you specify the sample rate like you've done, pulse will open the card at that rate and will resample all input (if necessary) to match that rate, so I think you're all set.

For the profile switching, this is something new in 0.9.15 which will try to determine automatically what profiles your sound h/w supports: e.g. can it handle recording and playback at the same time, can it handle 2 channel or 6 channel output (and in doing 6 channel output do you have to sacrifice recording capabilities etc). None of this info is not available directly from alsa so we have to probe and do a bit of guess work. Hot switching for profiles is possible now, but the UIs need to catch up.

Subscribe to the list (or just use gmane.org which is what I do) if you want to know more :)

Take care