BD 5.1 PCM Audio Clipping

I have a number of Blu-ray disc MakeMKV copies that have audio clipping issues when played with Infuse on an Apple TV. During loud scenes the audio becomes “scratchy”.

The problematic files all have PCM (pcm_s16le in ffprobe) 5.1 audio tracks. Files with DD or DTS 5.1/7.1 audio tracks don’t appear to have this issue.

I’ve tried connecting my ATV to:

  • a HDbaseT matrix, which does audio extraction
  • my TVs, directly (both LG and Samsung TVs)
  • a HDMI audio extractor box
  • LG PC monitor with HDMI IN
  • bluetooth headphones

Doesn’t matter how I get the audio out of the ATV, the sound is always distorted on these files.

I’ve tried adjusting various settings in the ATV settings, to no effect:

  • Video and Audio > Audio Format changed from Off to On and set New Format to Stereo
  • Video and Audio > Reduce Loud Sounds changed from Off to On
  • Video and Audio > Audio Mode changed from Auto to 16 bit

My Infuse setup is:

  • Apple TV 4k (A2169), running tvOS 15.1.1 (19J581)
  • Infuse Pro 7.2.1 (3874)

My media library hosted on Jellyfin. I’ve checked and no transcoding is occurring.

The audio is correct when the files are played with VLC for ATV.

Here are some sample files that reproduce the problem. These are from the Blu-ray of “Gone in Sixty Seconds”. The intro titles of this movie exhibit this issue.

bd-copy-trimmed.mkv. Raw source, trimmed with ffmpeg (ffmpeg -i /mnt/Media/Library/Blu-ray\ Movies/Gone\ in\ Sixty\ Seconds\ \(2000\).mkv -t 35 -c:v copy -c:a copy bd-copy-trimmed.mkv)

hdmi-recorded.wav. Audio from Infuse playing the original file on the ATV, captured using a HDMI audio extractor connected to the Line In of my PC.

probe.txt. Output of ffprobe for the original file. Audio track is listed as Stream #0:1(eng): Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, 5.1(side), s16, 4608 kb/s (default).

I’ll also mention that I don’t have a 5.1/7.1 surround setup. Only stereo speakers.

We have a fix for 16-bit PCM tracks coming in the 7.3 update.

Excellent. I’ll report back once 7.3 releases.