2015-02-04, 02:48
Hi Folks,
i just had a strange issue and just want to share my findings, in case anyone else has the same problem.
I use a LogiLink 7.1 USB Sound Box (see on LogiLink.com) to output SPDIF audio via Toslink to my Yamaha RX-V775. AC3 and DTS Passthrough work fine, but PCM 2.0 stereo puts some crackles above the music. But: If i connect the analog output of the Sound Box to my AVR, stereo is fine. So audio in principle arrives fine in the usb box, but still somehow the PCM output is messed up.
The Problem was choosing the correct audio device. My USB Sound Box is offered by kodi in three variants:
USB Sound Device (@:CARD=Device,DEV=0), Analog
USB Sound Device (surround21:CARD=Device,DEV=0) Analog
USB Sound Device, S/PDIF
Initially I chose the last one, S/PDIF, because I thought this was what I wanted.
After switching to the first one, everything works fine. The last one is still chosen as Passthrough device, of course. Clean 2.0 PCM sound and working passthrough multichannel audio. There is a downside though: The first device only offers 48000 Hz Sampling rate, hence all my 44100 Hz audio files will suffer from resampling... The second device offers also 44100, but sounds really strange.
So i guess the snd_usb_audio does not know this device really well...
Edit: I just had a look into the datasheet of the device found at the link above, and it clearly states the S/PDIF output to support only 48kHz. So when the "USB Sound Device, S/PDIF"-device offers 44100 Hz, this really is wrong and results in bad audio if played back at 44100 Hz. If I set it t the "USB Sound Device, S/PDIF"-Device to a fixed 48kHz, Stereo works fine, but passthrough is disabled. So in the end i am quite lucky that the first "USB Sound Device (@:CARD=Device,DEV=0), Analog" is indeed correct in reporting only 48 kHz so that it uses only 48 kHz even if not set to 'fixed' while still allowing passthrough (and AC3 transcoding if set to only 2.0 analog connections)
i just had a strange issue and just want to share my findings, in case anyone else has the same problem.
I use a LogiLink 7.1 USB Sound Box (see on LogiLink.com) to output SPDIF audio via Toslink to my Yamaha RX-V775. AC3 and DTS Passthrough work fine, but PCM 2.0 stereo puts some crackles above the music. But: If i connect the analog output of the Sound Box to my AVR, stereo is fine. So audio in principle arrives fine in the usb box, but still somehow the PCM output is messed up.
The Problem was choosing the correct audio device. My USB Sound Box is offered by kodi in three variants:
USB Sound Device (@:CARD=Device,DEV=0), Analog
USB Sound Device (surround21:CARD=Device,DEV=0) Analog
USB Sound Device, S/PDIF
Initially I chose the last one, S/PDIF, because I thought this was what I wanted.
After switching to the first one, everything works fine. The last one is still chosen as Passthrough device, of course. Clean 2.0 PCM sound and working passthrough multichannel audio. There is a downside though: The first device only offers 48000 Hz Sampling rate, hence all my 44100 Hz audio files will suffer from resampling... The second device offers also 44100, but sounds really strange.
So i guess the snd_usb_audio does not know this device really well...
Edit: I just had a look into the datasheet of the device found at the link above, and it clearly states the S/PDIF output to support only 48kHz. So when the "USB Sound Device, S/PDIF"-device offers 44100 Hz, this really is wrong and results in bad audio if played back at 44100 Hz. If I set it t the "USB Sound Device, S/PDIF"-Device to a fixed 48kHz, Stereo works fine, but passthrough is disabled. So in the end i am quite lucky that the first "USB Sound Device (@:CARD=Device,DEV=0), Analog" is indeed correct in reporting only 48 kHz so that it uses only 48 kHz even if not set to 'fixed' while still allowing passthrough (and AC3 transcoding if set to only 2.0 analog connections)