audio conversion channelmetadata missing

[bololo]

Hi,

I noticed that my audioconversions of film-audiotracks bei result in problems when playing on TV (Stereo)

Background music is too loud and spoken dialoges too silent.
Now I found these (see attached picture) audiometadata/channeldata are missing in the converted audio.

Sourceformat varies from AC3 eac or truehd. Targetformat should be opus.

Does anyone know a free (conversion)software that transfers this metadata to target file?

[tebasuna51]

That metadata are only in AC3/EAC3 format and can't be transferred to opus.

You need make a downmix to stereo with strong Center channel, low presence of Surround channels and without LFE channel.
What software do you use for your audioconversions?

[j7n]

This metadata is specific to AC-3 and is not found in other formats like Opus. It is always calculated by the official Dolby encoder and embedded into every piece of data throughout the file. Not just once, but many times. I think that no free AC-3 encoder calculates dynamic compression.

The metadata contains instructions on how to do downmix to stereo. Usually it is the same where surround is attenuated by 3 dB and center is attenuated by 3 dB (but added twice to both fronts). It can range between 0 and 6 dB. Other formats should use the same default downmix matrix without any instruction, but maybe they don't on the TV.

Are you downmixing during encoding or keeping the same number of channels? Maybe keep the AC-3 format if it works better on the TV. Usually there is AC-3 accompanying TrueHD.

[bololo]

Hi actually I am keeping the same amount of channels and let TV downmix to Stereo. But I assume because this information is lost I have the effects I wrote above.
Actually I just want to save some diskspace and make audiotracks smaller by switching to a algorithm that keeps high quality at low bitrates.
I tried Fre:ac and foobar with plugins so far, but I had not the idea to downmix to stereo.

I might have to try that.

[j7n]

It is possible that the channel order of Opus is not correctly understood by the TV. Some PC players had a problem with that. Compare a few formats. I would try to keep surround sound for the future if possible, as the space savings relative to the video size wouldn't be great.

[tebasuna51]

With foobar there are a Channel Mixer plugin, and can be configured like the image:

[bololo]

Thank you I will try that.

[bololo]

Unfortunately Channel Mixer DSP seems no more available.
I downloaded a dll and put it into component directory, but I recieve error: Not a valid 32bit application.
Did I wrong by copying it to this folder?
Any Alternatives?

Edit: I hat to switch to 32bit Foobar2000

[tebasuna51]

You are right, many ussefull plugins aren't ported to 64 bits. Also foo_dsp_downmix can't be used with the 64 bits version.
I have both foobar versions in my system but I never use the 64 bits.

You always have the ffmpeg command line.

You need a folder with ffmpeg.exe from here (https://ffmpeg.org/download.html#build-windows) and a SOURCE51 file to convert.
The SOURCE51 can be a track.ac3 or .dts, .eac3, and many more formats, with at least 5.1 channels (work also with 7.1)

Now execute in that folder:

ffmpeg -i SOURCE51 -vn -af "pan=stereo|FL<c0+c2+.5c4|FR<c1+c2+.5c5" -acodec libopus -ab 160k OUTPUT.opus

You can select also the desired bitrate (here 160 Kb/s). Also you can convert the full movie with a video copy and convert the first audio track

ffmpeg -i YOURMOVIE -map 0:v -c:v copy -map 0:a:0 -af "pan=stereo|FL<c0+c2+.5c4|FR<c1+c2+.5c5" -c:a libopus -ab 160k OUTPUT.mkv