Hi everybody, my first post and all I installet Lion the other day and now I have encountered a sound issue in iTunes and QuickTime. I have a ATV2 that I use to stream content to, and I use MKVtools to convert all MKV-files. Since the upgrade to Lion the sound in m4v-files that uses 5.1 AAC channels comes out silent or just disturbing "clicks". If the file is m4v with 2 channels, or mp4 with 5.1 or 2 channels it seems to work just fine. When I use MKVtools to convert MKV-files I use passthru on the h264 video, and use AAC 5.1 for sound (no 2 chan fallback). Most often I remember to set the "Device" option to Apple TV, which seems to trigger the .m4v file format instead of .mp4. The files converted with device setting "General" and produces the .mp4 files works just fine in both iTunes and QuickTime. I have tried altering the sound output in the Sound/MIDI-app with no luck. The weird is that if I open one .m4v (h264/5.1AAC) and one .mp4 (h264/5.1AAC) in quicktime and open the "video info window" (don't know what is called in the english OS since I use Swedish) the encoding is exactly the same, but the sound in the .m4v is dead. It works to airplay the .m4v files to my ATV2, it is just in my Mac the sound isn't working.. I tried just to change the filename from .m4v to .mp4 but that didn't work. Enyone know of a workaround/fix for this?