[Updated 2019] Opus 1.3. New WebM audio codec (Opus+VP9/AV1)

[qyot27]

Ah, here it is in opusenc's manpage:
--serial n

Force use of a specific stream serial number, rather than one that is randomly generated. This is used to make the encoder deterministic for testing and is not generally recommended.
You could try forcing the serial number and see if that results in what you're wanting.

[redbtn]

Ah, here it is in opusenc's manpage:

--serial n



Force use of a specific stream serial number, rather than one that is randomly generated. This is used to make the encoder deterministic for testing and is not generally recommended.

You could try forcing the serial number and see if that results in what you're wanting.I don't know what number I should use. It seems to me like it just stream "ID", isn't it?

[qyot27]

If you look at opusinfo's output, serial numbers appear to be CRC32-style hashes:
E:\Documents>opusinfo test.opus | grep serial
New logical stream (#1, serial: dc7ac5e3): type opus

[Boulder]

What is the proper way to re-encode a 3/1-channel track with Opus? At least Mediainfo thinks Opus maps two channels to the rear while the proper order is L R C Cb.

[tebasuna51]

Seems opus only support these channels mapping:

5.1.1.2. Channel Mapping Family 1

Allowed numbers of channels: 1...8. Vorbis channel order.

Each channel is assigned to a speaker location in a conventional
surround arrangement. Specific locations depend on the number of
channels, and are given below in order of the corresponding channel
indices.

o 1 channel: monophonic (mono).

o 2 channels: stereo (left, right).

o 3 channels: linear surround (left, center, right).

o 4 channels: quadraphonic (front left, front right, rear left,
rear right).

o 5 channels: 5.0 surround (front left, front center, front right,
rear left, rear right).

o 6 channels: 5.1 surround (front left, front center, front right,
rear left, rear right, LFE).

o 7 channels: 6.1 surround (front left, front center, front right,
side left, side right, rear center, LFE).

o 8 channels: 7.1 surround (front left, front center, front right,
side left, side right, rear left, rear right, LFE).

[filler56789]

What is the proper way to re-encode a 3/1-channel track with Opus? At least Mediainfo thinks Opus maps two channels to the rear while the proper order is L R C Cb.

Vorbis, Opus, AAC, FLAC, are good only as replacements for the old Layer 3,
if you want PROPER multichannel encoding just go with AC3, DTS, MLP /TrueHD and DTS-HD.

[Richard1485]

Another option is to double the back channel and encode as 5.0.

[Boulder]

Another option is to double the back channel and encode as 5.0.

Yes, that's what I thought I'd have to do if Opus couldn't work with the original order. I recall that the eac3to thread had at least one case like this, just have to dig the magic Avisynth script from there :)

[tebasuna51]

You can use:

ffmpeg -i input310 -af "pan=5.0|FL=FL|FR=FR|FC=FC|BL=0.707BC|BR=0.707BC" -ab 192k output50.opus

But warning, MediaInfo v20.09 have a bug and inform output50.opus like:
Channel layout : L R Lb Rb LFE
a inexistent opus channel layout

But after decoded output50.opus by ffmpeg or opusdec have the correct channel mapping:
Channel layout : L R C Lb Rb

[Boulder]

You can use:

ffmpeg -i input310 -af "pan=5.0|FL=FL|FR=FR|FC=FC|BL=0.707BC|BR=0.707BC" -ab 192k output50.opus

But warning, MediaInfo v20.09 have a bug and inform output50.opus like:
Channel layout : L R Lb Rb LFE
a inexistent opus channel layout

But after decoded output50.opus by ffmpeg or opusdec have the correct channel mapping:
Channel layout : L R C Lb Rb
Cheers, I was already wondering the channel layout and figured that I may have to add an empty LFE track there but it seems to be working then :)

[Richard1485]

Tebasuna has already provided an easy solution with ffmpeg, but if anyone wants to go from 4.0 to 5.0 with AviSynth:

#double back channel
fl=WavSource("l.wav")
fr=WavSource("r.wav")
c=WavSource("c.wav")
bc=WavSource("bc.wav").Amplify(0.707)# preserve global volume

MergeChannels(fl,fr,c,bc,bc)

[Boulder]

I think you also need to use Amplify(0.707) on those new rear channels.

[tebasuna51]

In order to obtain a correct channel mapping from AviSynth I recommend use BeHappy with this .avs:

a=LWLibavAudioSource("INPUT310")
fronts = GetChannel(a, 1, 2, 3)
back = GetChannel(a, 4).Amplify(0.707)
Mergechannels(fronts, back, back)

And check the ChMask option with a value of 55.
Now the AviSynth output is a WAVE_FORMAT_EXTENSIBLE with the correct channelmask and must be encoded correctly by any encoder compatible (ffmpeg,qaac,opus,flac,...)

[EDIT] If you don't want install BeHappy you can try this command line:

wavi INPUT310.avs - /M 55 | opusenc --ignorelength --bitrate 192 - output50.opus

I attach the last Chikuzen wavi encode (https://forum.doom9.org/showthread.php?p=1527102#post1527102)
There are also rewavi (https://forum.doom9.org/showthread.php?p=1829561#post1829561) with similar sintax:

rewavi INPUT310.avs - -x 55 | opusenc --ignorelength --bitrate 192 - output50.opus

Out of BeHappy the default AviSynth output is 16 bits, if you want more precission you can add to .avs the line:
global OPT_AllowFloatAudio=True

And also Avs2pipemod (http://avisynth.nl/index.php/Avs2pipemod)

Avs2pipemod INPUT310.avs -extwav=float | opusenc --ignorelength --bitrate 192 - output50.opus

It can work here because the default channel mask for 5 channels is 55 but Avs2pipemod can't supply the desired channel mask like wavi/rewavi

For big files maybe the wavi-AviSynth 32 bits can crash.

[Richard1485]

I think you also need to use Amplify(0.707) on those new rear channels.

Oh, yes! Good point.:D