Audio distortion in VLC when playing select video files

[digifuzzy]

Pre 1.4-release. VLC and all other audio would play back without any indication of error.

Hardware is functional. No error messages in dmesg for audio device. In VLC only(v3.0.7.1), playback of some video files(mp4, mkv) produces distorted sound(voices are mechanical, slight slur and tinny echo, correct pitch).  Adjusting audio delays(j/k key) has no effect on sound quality. Reverted to previous version (3.0.6-r1), which was known to be working pre-1.4-release, produced same kind of sound problem. Audio issues are not present in other applications nor in VLC when playing a music file(mp3, ogg, et al) or avi video files. I have rebuilt library dependencies for VLC.

Help?

EDIT: this should be in "desktop" group.

[digifuzzy]

For the intrepid web searcher looking to solve this problem for themselves, here's what I did...
- VLC (v3.0.7.1) downgraded v3.0.6.x (no change)
- restored VLC to latest and re-installed ffmpeg, x264, x265, et al (no change)
- discovered that ffmpeg has command line access (`$ ffplay [filename]) - audio normal and no distortion
- recalled VLC had similar functionality (`$ cvlc [filename]) - distortion

All this was going on concurrent to situation with determination of correct video card settings (see forum post Confirm Video Card Settings - 1.4-release)

Discovered that video audio hardware acceleration (USE flag `vaapi` was not set in the profile for my card)

Bug FL-6636 and PR# 155 issued to address.

tl;dr - check USE flags are correct for your HW (AMD cards r100/r200 and earlier, r300->r500, r600->N.Islands, S.Islands and later)
Flags to confirm vdpau, vaapi.

Fingers crossed, but I believe this will resolve the problem for me. Recompiling...