$ mpv \
  --audio-channels=5.1,stereo \
  --audio-spdif=ac3,eac3,dts-hd,truehd \
  --audio-device=alsa/hdmi:CARD=PCH,DEV=0 \
  audiofile.mp4

Fant tipset på https://forum.manjaro.org/t/how-do-i-enable-surround-sound-in-pulseaudio/56394.

Oppdatering 27.09.2023

Jeg støtte i dag på et tilfelle med en videofil med 6-kanals lyd, men hvor avspilling med kommandoen ovenfor ikke ga noen lyd over HDMI.

Uttrekk fra ffprobe gir meg:

Input #0, matroska,webm, from ...
  Metadata:
    encoder         : libebml v1.4.2 + libmatroska v1.6.4
[...]
    Stream #0:1(eng): Audio: eac3, 48000 Hz, 6 channels, fltp
    Metadata:
      title           : English
      BPS             : 384000
      DURATION        : 02:49:17
      NUMBER_OF_FRAMES: 317427
      NUMBER_OF_BYTES : 487567872

mpv-avspilling rapporterte 2-kanals lyd: AO: [alsa] 48000Hz stereo 2ch spdif-ac3.

MPV AD-parameter (Audio Decoder)

Jeg fikk surround-lyd med AD-parameteren (Audio Decoder):
--ad=spdif:ac3,spdif:dts,

mpv rapporterte AO: [alsa] 48000Hz 5.1 6ch s32 og receiveren min viste MULTI-CHANNEL lyd-input.

MPV AF-parameter (Audio Filters)

Jeg prøvde også med noen AF-parametere (Audio Filters):

  --af=lavcac3enc
  --af=scaletempo,lavcac3enc=yes:640:3

, men i begge tilfeller rapporterte mpv om AO: [alsa] 48000Hz stereo 2ch spdif-ac3, selv om receiveren min identifiserte det som Dolby Digital. Også i kombinasjon med --ad-parameteren. Jeg gjorde ingen test på om det faktisk ble ekte surround-lyd fra receiveren.

Kilder

Fant tipsene fra:
1) Does anyone has realtime ac3 or dts encoding running? (Archlinux)
2) New To MPV. Trouble with EAC3 6 channel audio. (Reddit)

Since then I have had varying success capturing hours of video from both Hi8 and VHS sources. Often lavrec will exit in the middle of a recording with somewhat unknown error messages such as:

# dmesg:
DC10plus[0]: jpg_sync - timeout: codec isr=0x00

# lavrec:
Error syncing on a buffer: Timer expired

… and other nicies.

Often this happened between recordings on the tape, when stopping and starting a recording, where it often occur a lot of noise and jitter. It happened more often when recording from VHS tapes than from HI8 tapes.

I tried different values for the system configuration kernel.sched_time_avg with what looks like random improvements. The default is 1000 on a normal Ubuntu Desktop 10.10. I have tried both 100 and 250, and 250 is what I am currently using. Change it like this:

$ sudo sysctl kernel.sched_time_avg=250

I was previously using KDE while recording, but found out that several background processes like Akonadi Server was running and stealing resources. The window manager seemed slow. I guess I have an I/O issue somewhere, but I just don’t know where. Maybe the SCSI drive or maybe the graphics card which is an old ATI Radeon 8500.

I an now running Openbox with Konsole, as a command line (in an X server) is all I need to both record and watch the result with mplayer afterwards. I feel it goes a little bit smoother.

The most effect, as I figured out, was setting the quality option of lavrec a little lower. Recording with the quality set to 100 might result in unstable recording with lost frames if there is the slightest delay in the system, and eventually lavrec just exits with an error.

I tried setting the quality to 80, just to give it a try, and it was recording much more smoothly with less dropped frames. It looks like lavrec now handles jitter much better.

I am now trying out a quality of 90 which also seems good. A little lost frames now and then, but I guess that occurs mostly between recordings since I am able to record several minutes from a single scene without a single frame drop.

This is the command I use now:

$ aoss lavrec --mjpeg-buffers 512 --mjpeg-buffer-size 8192 -f q -d 1 -i p -q 90 -s -R l -U "dc10-%02d.mov"

So, my best tip to avoid lost frames and lavrec crashes is to lower the quality a little.

First, the camcorders charger is broken, and buying a new one is kind of difficult, but luckily, I got to borrow one from some friends.
Second, I managed to find the last working VHS player I got. A little dusty.
Third, since Mini-DV is kind of legacy as well, I decided to copy those on to my computer as well, if I ever manage to find the camcorder. Got the charger, remote and the casing, but no camcorder. Oh well…

Find the best composite or S-Video cables you can dig up, because this job you only want to do once. I got my overly priced Monster composite cables, ready to start. Soon…

Ok, so I’ve got an analog video capture card that I, in the old days, used with Windows 98 and pulled my hair out to get working on Windows 2000. The card is a Zoran based Pinnacle/Miro DC10+. That’s history. Sort of. I still got the video capture card.

What I also got is the latest Ubuntu Linux 10.10, also known as Ubuntu Maverick, which comes with the somewhat great ALSA audio support. I say somewhat because this version of Ubuntu lacks the legacy OSS compability driver in the Linux kernel. In other words it makes it harder to record or play audio from older kinds of programs, such as lavrec.

lavrec is the video and audio capture application from the MJPEG video tools package. It is the tool recommended for capturing video from the DC10+ card on Linux, but it lacks ALSA support. However, you can get a OSS wrapper program named aoss from the Ubuntu alsa-oss package which provides OSS is most cases for those old applications.

This is how I do video and audio recording, from the command line, enter something like this:

$ aoss lavrec -f a -i p -q 100 -s -R l -U dc10-out.avi

Make sure that the correct recording input line is selected for CAPTURE in alsamixer -V capture such as Line or Mic. I recommend you capture a 10 second test and check the sound.