Audio passthrough testing

  • Sorry, but it's impossible to debug something that works for me. I tested this on LG B8 TV, which supports most of compressed formats. AVRs are known to cause issues, but I have none.

  • Hi !

    I did tests with my Oprange pi PC, I have a AVR Denon AVR-S730 and passthrough work not too bad at all


    Dolby Digital : OK

    Dolby Digital Plus : OK

    DTS : OK

    DTS-Hd : OK but a lot of clipping (cracking/popping, I don't know the good word in english, this append also with H6)

    TRUE-HD : not tested


    A really weird bug : If a disable AC3 transcoding, I set the number of channel to 7.1 and I watch an episode or a movie in AAC 5.1, I hear only the background music, no dialog... But if I set number of channel to 2.0 and I enable AC3 transcoding everything is fine.


    Another thing, with the "not passthrough release" I have a lot of sound cut, it's totally random it's really disturbating but with the passthrough relesase I have no sound cut.


    So personnally, passthrough edition is my favorite release, I disable DTS-HD and TRUE-HD passthrough, I enable AC3 transcoding and everything work pretty well.

    Libreelec : Raspberry 4, Orange pi lite2, Orange pi PC(and +), Pine H64, Rock64, RockPro64, soon Orange Pi 3 and PC2

    Divers : NVidia Shield Pro, NVidia Shield Tube, N2 and C4

    Edited once, last by mike2002 ().

  • Sorry, but it's impossible to debug something that works for me. I tested this on LG B8 TV, which supports most of compressed formats. AVRs are known to cause issues, but I have none.

    Thanks for your great work. It seems to be some race condition, considering that it works on another Opi PC, maybe it works in a future version again, as it did in the one from last September. As long as the normal version works, I am happy 😊

  • It seems to be some race condition, considering that it works on another Opi PC

    I don't think it's issue with board - there is no real difference regarding HDMI audio, I think it's end equipment. Just for that reason, I sometimes test with different monitors and TVs. This allowed me to fix most bugs, but obviously I don't have all quirky monitors/TV... Do you have a possibility to test passtrough on some TV which supports compressed formats directly, without AVR?

  • A really weird bug : If a disable AC3 transcoding, I set the number of channel to 7.1 and I watch an episode or a movie in AAC 5.1, I hear only the background music, no dialog... But if I set number of channel to 2.0 and I enable AC3 transcoding everything is fine.

    After recent investigation, I found out that this makes perfect sense. ALSA config is written in such way, that all audio is transcoded in IE958 format. This is a bit problematic - DW-HDMI IEC958 support is meant only for compressed formats, 2 ch for normal compressed streams, 8 ch for HBR. It's unclear at this point if any other channel combination may work with IEC958 format. With AC3 transcoding you make sure that there is no uncompressed audio, so IEC958 should work fine in all cases. GUI uses stereo sound, which should work with IEC958 too.