opdenkamp/xbmc — Issue #451: Multichannel AAC is downmixed to 2 channel PCM over SPDIF
Author: alktlr
Created: 2012-03-02 21:24:59+00:00
State: open

My IPTV provider broadcasts video and audio in different formats and combinations. But I have noticed multichannel AAC is downmixed to 2 channel PCM over SPDIF. I know surround sound is working fine when audio is in AC3, as it is just passed through.

The funny thing is that a recorded program on the same channel with multichannel AAC is transcoded to multichannel Dolby Digital when played back in XMBC?!?

This the error that I'm getting in Live TV:
21:25:29 T:140545731860224 ERROR: CDVDAudioCodecPassthroughFFmpeg::Open - FFmpeg SPDIF muxer does not support this codec
21:25:29 T:140545731860224 NOTICE: Creating audio device with codec id: 86018, channels: 6, sample rate: 48000, no pass-through

Same channel played back from Recordings:
21:53:45 T:140545631147776 NOTICE: Creating audio device with codec id: 86019, channels: 6, sample rate: 48000, pass-through

AAC icon is shown in channel information OSD for both live tv and recordings, so it is safe to say it is not transcoded by tvheadend.

Software used:
XBMC 2:11.0-pvr+p8~git20120219.26797f4-0ubuntu1~stable67~oneiric
tvheadend 2.12.99~pulse-4

Let me know if you need anything else.