[mythtv-users] Surround sound issues w/ digital passthrough

Richard Shaw hobbes1069 at gmail.com
Sun Feb 20 03:42:09 UTC 2011


I've been having some quirky issues with sound. At least twice I've
had to go into the setup and re-enable passthrough and 5.1 speaker
arrangement. I'm assuming that happened after updates but I don't know
why updates would have changed my settings. Anyways, that's not the
main problem as reconfiguring fixed it.

Now I have everything setup correctly (i.e. I haven't changed anything
in the audio settings) and I'm no longer getting surround sound. At
first I just thought it was the broadcast itself (ATSC w/ HDHomerun)
as I've noticed several programs using 2 channel Dolby Digital instead
of 5.1 by checking the display on my receiver.

Now my receiver just shows PCM and does not give a channel count so it
appears myth is down-mixing to 2-channel PCM stereo.

I've checked the log file and I didn't see anything that jumped
out at me as it did identify the audio stream as AC3 and showed my
audio device capable of AC3 and DTS passthrough. See below for the nitty-gritty.

Here's my settings:

- Audio device: ALSA:iec958:CARD=SB,DEV=0
- DD and DTS boxes checked
- Speaker configuration: 5.1
- Upmix stereo to 5.1 unchecked
- Advanced audio config: unchecked
- Internal volume controls: unchecked

Also, anyone else have a problem with some of the check boxes being
squished and lack of highlighting on check boxes?

Thanks,
Richard

log file w/ -v important,audio,playback:
2011-02-19 21:03:17.797 TV: StartTV() -- begin
2011-02-19 21:03:17.797 TV: ctor -- begin
2011-02-19 21:03:17.812 TV: ctor -- end
2011-02-19 21:03:17.812 TV: Init -- begin
2011-02-19 21:03:17.819 TV: DrawUnusedRects() -- begin
2011-02-19 21:03:17.820 TV: DrawUnusedRects() -- end
2011-02-19 21:03:17.820 TV: Init -- end
2011-02-19 21:03:17.821 TV: tv->Playback() -- begin
2011-02-19 21:03:17.831 TV: tv->Playback() -- end
2011-02-19 21:03:17.831 TV: StartTV -- process events begin
2011-02-19 21:03:17.925 TV: HandleStateChange(0) -- begin
2011-02-19 21:03:17.929
RingBuf(/var/lib/mythtv/1241_20110219190000.mpg):
OpenFile(/var/lib/mythtv/1241_20110219190000.mpg, 2000 ms)
2011-02-19 21:03:17.942 TV: DrawUnusedRects() -- begin
2011-02-19 21:03:17.942 TV: DrawUnusedRects() -- end
2011-02-19 21:03:17.942 TV: StartPlayer(0, WatchingPreRecorded, main) -- begin
2011-02-19 21:03:17.942 TV: Elapsed time since TV constructor was called: 145 ms
2011-02-19 21:03:18.546 Pulse: Operation: success 1 remaining 1
2011-02-19 21:03:18.566 Pulse: Operation: success 1 remaining 0
2011-02-19 21:03:18.583 AO: Sample rate 44100 is supported
2011-02-19 21:03:18.584 AO: Sample rate 48000 is supported
2011-02-19 21:03:18.584 AO: Sample rate 88200 is supported
2011-02-19 21:03:18.584 AO: Sample rate 96000 is supported
2011-02-19 21:03:18.584 AO: Sample rate 192000 is supported
2011-02-19 21:03:18.584 AO: 2 channel(s) are supported
2011-02-19 21:03:18.606 AO: AC3 or DTS capable
2011-02-19 21:03:18.606 AO: 6 channel(s) are supported
2011-02-19 21:03:18.610 AO: Killing AudioOutputDSP
[SNIP video stuff]
2011-02-19 21:03:18.686 AFD: Stream #1, has id 0x34 codec id AC3, type
Audio, bitrate 384000 at 0x427f4b0
2011-02-19 21:03:18.687 AFD: Looking for decoder for AC3
2011-02-19 21:03:18.687 AFD: Audio Track #1 is A/V stream #1 and has 2
channels in the English language(6647399).
2011-02-19 21:03:18.688 AFD: Selected track 1: English AC3 2ch (A/V Stream #1)
2011-02-19 21:03:18.688 AFD: Initializing audio parms from audio track #1
2011-02-19 21:03:18.688 AFD: Audio format changed
			from id(NONE)     -1Hz -1ch -1bps     to id( AC3)  48000Hz  2ch 16bps
2011-02-19 21:03:18.688 AO: Killing AudioOutputDSP
2011-02-19 21:03:18.846 Pulse: Operation: success 1 remaining 1
2011-02-19 21:03:18.867 Pulse: Operation: success 1 remaining 0
2011-02-19 21:03:19.047 Pulse: Operation: success 1 remaining 1
2011-02-19 21:03:19.067 Pulse: Operation: success 1 remaining 0
2011-02-19 21:03:19.083 AO: Sample rate 44100 is supported
2011-02-19 21:03:19.083 AO: Sample rate 48000 is supported
2011-02-19 21:03:19.083 AO: Sample rate 88200 is supported
2011-02-19 21:03:19.083 AO: Sample rate 96000 is supported
2011-02-19 21:03:19.083 AO: Sample rate 192000 is supported
2011-02-19 21:03:19.083 AO: 2 channel(s) are supported
2011-02-19 21:03:19.105 AO: AC3 or DTS capable
2011-02-19 21:03:19.105 AO: 6 channel(s) are supported
2011-02-19 21:03:19.106 AO: Killing AudioOutputDSP
2011-02-19 21:03:19.106 AO: Original codec was AC3, signed 16 bit, 48
kHz, 2 channels
2011-02-19 21:03:19.106 AO: enc(0), passthru(0), canAC3(1), canDTS(1),
canLPCM(0), configured_channels(2), 2 channels supported(1)
2011-02-19 21:03:19.107 ALSA: SetParameters(format=2, channels=2,
rate=48000, buffer_time=200000, period_time=50000)
2011-02-19 21:03:19.107 ALSA: Buffer time = 200000 us
2011-02-19 21:03:19.107 ALSA: Period time = 50000 us
2011-02-19 21:03:19.109 ALSA: Buffer size = 9600 | Period size = 2400
2011-02-19 21:03:19.111 AO: Audio fragment size: 4800
2011-02-19 21:03:19.111 AO: Audio Stretch Factor: 1
2011-02-19 21:03:19.112 AO: Ending Reconfigure()
2011-02-19 21:03:19.112 AudioPlayer: Enabling Audio
2011-02-19 21:03:19.112 AO: Reconfigure(): No change -> exiting
2011-02-19 21:03:19.112 AO: kickoffOutputAudioLoop: pid = 7977
2011-02-19 21:03:19.112 Dec: Selected track #1 in the Unknown language(0)
2011-02-19 21:03:19.112 AO: OutputAudioLoop: Play Event


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