XO-1.75 activity and application audio sounds raspy

[greenfeld]

Output audio in Speak, etc. sounds raspy on an XO-1.75. This could be a sampling/aliasing issue like the OFW sound, some sort of underrun/overrun issue, or something else.

Written up separately from #10831 for clarification due to the number of complaints coming in about it.

[tonyforster]

dup of #11170

[greenfeld]

Replying to tonyforster:

dup of #11170

Not necessarily; #11170 has turned more into an boot chime/Open Firmware ticket; this is more of a Linux/ALSA/userspace ticket.

They could be combined but I suspect from my limited audio hardware knowledge that the fixes are somewhat independent.

[wad]

One source of this problem has been identified by the Quanta team. The trace impedances on the XO-1.75 right speaker are too large, providing a large ringing on that speaker.

This will be fixed on C1 pre-production models.

The other problem identified by Mitch in #11170 will also affect Linux applications. That is the lack of digital anti-aliasing when operating at lower sample rates. One suggestion to fix the problem is to remove support from the Linux driver for the lower sample rates, only allowing 22.05 or higher. I assume that since applications on XO-1.5 dealt with a fixed 48 kHz, this is handled by a higher layer of software ?

[greenfeld]

Most voice codecs have sampling rates below 22.05 kHz.

Has anyone regularly used these on XOs? And if so does the XO-1.5 have a similar limitation?

[wad]

Replying to greenfeld:

Most voice codecs have sampling rates below 22.05 kHz. Has anyone regularly used these on XOs? And if so does the XO-1.5 have a similar limitation?

Don't confuse the channel sampling rate with the playback rate. Just because a voice coded bandlimits and drops the sampling rate before encoding doesn't mean that the decoded audio isn't upsampled to a higher frequency before playback.

In XO-1.5, the HD Audio codec only supported 48 KHz or higher. Somewhere in our middleware (GStreamer ?) software is upsampling any lower resolution audio before playback.

[Quozl]

Clicking during audio output heard using Speak on os6.

[tonyforster]

Though #11170, the boot chime, sounds ok, speak is still clicky in os7. Must admit though, its a bit subjective.