mythmusic: 88.2KHz/24bit/6ch FLAC/WAV distorts

[ignissport@…]

88.2KHz/24bit/6ch becomes distorted on playback when played in mythmusic. This occurs in both FLAC and WAV formats.

I've replicated this on two machines with very different hardware setups. One was an Audigy 2 ZS running through headphones over pulseaudio, the other was an onboard SP/DIF direct to an external amp (no pulse). Both played other formats fine, but heavily distorted when playing FLAC/WAV in this specific sample rate/bit depth/channel.

44.1KHz/16bit/Stereo plays fine. 48KHz/16bit/Stereo plays fine. 88.2KHz/24bit/Stereo plays fine. 88.2KHz/16bit/6ch plays fine. 96KHz/24bit/Stereo plays fine. 96KHz/24bit/6ch plays fine.

It's just 88.2KHz/24bit/6ch that distorts. If I re-encode the FLAC/WAV as 16bit, it plays back fine.

The FLAC/WAV also plays fine in other media players (including mythffplay) and passes a "flac -t" test.

mythffplay output: (a file that distorts) Audio: flac, 88200 Hz, 6 channels, s32

(a file that does not distort) Audio: pcm_s16le, 88200 Hz, 6 channels, s16

I suspect this may have something to do with changes introduced ticket #9930, but I can't be sure.

Both test machines are running v0.24.1-96-ge89d6a9 branch fixes/0.24

I've marked it as low/trivial as I suspect I'm the 0.0001% of the population that actually has media in this format.

[paulh]

Is this still a problem with current master?

I just tried 3 random flac files that I could find all with 88.2KHz/24bit they all played fine in MythMusic but couldn't find any 6 channel ones to test, the closest I could find was one that was flagged as Audio: flac, 88200 Hz, 5.1(side), s32 don't know if that is the same as the 6 channel ones you had problems with?

Incidentally mythffmpeg had problems playing that file and mythavtest played it but seemed to jump about randomly while playing it. MythMusic played it without problems though.

[ignissport@…]

You may be right. 88.2KHz/24bit/6ch seems to be playing for me now. However, I recently changed hardware from SP/DIF to HDMI (new amp), which means that it's now sending raw 6ch PCM to my receiver rather than converting to Dolby Digital on-the-fly.

I've thrown together a test suite to test *ALL* the formats. I've only got 1Mbps of upload bandwidth, so it may take a while to download the higher res ones. ​http://planetexpress.homelinux.com/~russell/SampleRateTestSuite/

I've recently formatted my other PC (now on Raring Ringtail), and I'm yet to install MythTV on it to re-test. I'll try and run both PCs through the test suite in the near future and post back with results.

[ignissport@…]

I've run through all of the above tests on two different systems.

They all played perfectly on my HTPC over HDMI.

On my desktop machine, the following two produced a noticeable distortion:

• 48KHz/16bit/6ch
• 96KHz/16bit/6ch

It sounded a lot like clipping. The desktop machine config:

• Mythtv fixes/0.26 (from ppa) v0.26.0-138-g69cd78b
• Creative Labs SB Audigy 2 ZS [SB0350]
• Stereo headphones
• Ubuntu 13.04 Raring Ringtail 64bit
• Audio Output Device: "ALSA:pulse"
• Speaker Configuration: Stereo

All files played OK in rhythmbox on the same machine.