Hi Chris,
please follow two important rules on mailing lists:
1. Always reply to all. If you're worried about the size of a text
attachment, use a pastebin.
2. Do not top-post.
On 10.09.2012 01:01, chris hermansen wrote:
> Thank you very much for your kind help and offer of assistance.
>
> I have zero experience around the kernel, so if you are prepared to
> send me a patch, that would be superb.
Sure. I attached one.
> A question (from my level 0 perspective): can I not patch the kernel I
> have, as opposed to getting one "unknown" to my current ubuntu
> distribution? (or maybe I am so clueless I just don't understand what
> you are suggesting below).
This can be confusing when you do it the first time, but no worries. It
has been the first time for everyone once :)
Run
git clone git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
Use "git patch" to apply the patch attached to this email.
Then follow these rules to get a kernel package that you can install on
your Ubuntu:
https://help.ubuntu.com/community/Kernel/Compile
> I am responding directly / just to you as the output of the lsusb is
> some 1600 lines and it seems imprudent to send it to the list as a
> whole.
Thanks for the thought. But again - please keep to the rules that are
established around here and that I described above.
> Also, the people at Schiit seem to be most approachable and I wonder
> if it would help others to provide some of this information to them,
> "once it's working" - what do you think?
Once we have a workaround, we can as well share it with them, sure.
Best regards,
Daniel
> On Sun, Sep 9, 2012 at 2:47 PM, Daniel Mack <zonque@xxxxxxxxx> wrote:
>> Hi,
>>
>> On 09.09.2012 23:26, chris hermansen wrote:
>>> I recently acquired a Schiit Bifrost and have been attempting to
>>> achieve (what I would call) "bit perfect" performance with 16 and 24
>>> bit music files at 44.1, 96 and 192K over the USB interface.
>>
>> [...]
>>
>>> In all of these cases, I end up with results that appear to be the
>>> same, or at least differ in ways indistinguishable to me. To
>>> elaborate, if I play a 16bit/44.1K FLAC file, then switch to a 24 bit
>>> and/or higher resolution file, the audio for the second file is
>>> garbled in a very distinctive way - it sounds like it is being passed
>>> through some sort of "distortion network". The basic nature of the
>>> melody is apparent, but everything sounds really odd. If I stop the
>>> second song and restart it, often on this second try it will play
>>> fine. Sometimes I have to do this more than once to get it to play
>>> fine.
>>
>> I have dealt with a number of USB audio interfaces lately that have
>> similar problems under Linux.
>>
>> The reason, as far as I could track it down, is that these interfaces do
>> not properly flush their feedback endpoint buffers when switching from
>> one sample rate to another, which results in wrong data being sent after
>> each stream start. The Linux driver has code for feedback format
>> auto-detection which gets confused by that and assumes a different
>> format, consequently sending data at a wrong rate.
>>
>> Some of these issues have been resolved by fixing the firmwares of
>> affected devices, for others I just recently submitted a patch that
>> makes the driver ignore the first n packets of a stream, to work around
>> that hardware bug:
>>
>>
>> https://git.kernel.org/?p=linux/kernel/git/tiwai/sound.git;a=commit;h=2b58fd5b
>>
>>> If anyone has any suggestions, I am willing to experiment (carefully)
>>> and document results.
>>
>> Yes, you could try building a kernel from
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
>>
>> And add a quirk to sound/usb/quirks.c, in function
>> snd_usb_endpoint_start_quirk(). Just add a check for your device's USB
>> VID/PID and do the same "ep->skip_packets = 4" for the SYNC endpoint.
>>
>> If you're not sure what to do, send me the output of "lsusb -v" on your
>> system and I'll provide a patch.
>>
>>
>> Thanks,
>> Daniel
>>
>
>
>
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 0f58b4b..5260d5b 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -770,6 +770,13 @@ void snd_usb_endpoint_start_quirk(struct snd_usb_endpoint *ep)
if ((le16_to_cpu(ep->chip->dev->descriptor.idVendor) == 0x23ba) &&
ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
ep->skip_packets = 4;
+
+ switch (ep->chip->usb_id) {
+ case USB_ID(0x0d8c, 0x0304): /* CMEDIA - Schiit USB Interface */
+ if (ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
+ ep->skip_packets = 4;
+ break;
+ }
}
void snd_usb_ctl_msg_quirk(struct usb_device *dev, unsigned int pipe,
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