How do I turn a mono MKV into a stereo?

[twogurusindrag]

I have an old TV special in MKV format, but there's only sound on the left side. I'm wondering how to go about getting sound on both sides? Thanks.

[harrylime]

If it's only in left then it's already stereo, just not properly mapped from a mono source (quite common for analogue transfers as then the L channel functions as the mono carrier). To help further I would need to know the exact details, as MKV is not a format but merely a container, it doesn't tell you the formats of the tracks inside of it (video, audio, etc). Could you use mediainfo or ffmpeg to display the file's properties and share them here?

[twogurusindrag]

Ricky Jay MediaInfo.png (82.94 KiB) Viewed 338 times

[harrylime]

Sadly with AAC there's no other option then to re-encode (just the audio of course), for example with ffmpeg:

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ffmpeg -i original.mkv -map 0:v -map 0:a -c:v copy -af "pan=mono|c0=c0" -c:a libfdk_aac -b:a 192k fixed_audio.mkv

that does rely on the officially paid codec libfdk_aac, if it isn't available in your ffmpeg then you could simply use 'aac' to use its built-in aac encoder with slightly less quality. Another option is to just decode to wav using 'pcm_s16le',

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ffmpeg -i original.mkv -map 0:v -map 0:a -c:v copy -af "pan=mono|c0=c0" -c:a pcm_s16le fixed_audio.mkv

or 'flac' to keep it losslessly compressed to save space (wav uses around 635 MB for an hour of audio, flac 200-300ish MB depending on the content).

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ffmpeg -i original.mkv -map 0:v -map 0:a -c:v copy -af "pan=mono|c0=c0" -c:a flac fixed_audio.mkv

However with flac it could be that some players will have compatibility issues as it's not a common format to use with video.

[twogurusindrag]

That's Greek to me.

[Rickenbacker325]

I have an old TV special in MKV format, but there's only sound on the left side. I'm wondering how to go about getting sound on both sides? Thanks.

What I’ve done is drop the file into a video editing program(Like iMovie or Final Cut..yes I use a Mac)…and separate the audio…fly that audio into a program like audacity and kill the dead channel and have one proper mono channel.

[Lord Reith]

Use https://xmedia-recode.de/en/

Set format to "matroska"
Set video mode to "copy"
Set audio mode to "convert" and choose codec "flac"
Under audio tab "channel mapping" set "channel order mode" to "custom" , leave "channel 1" as "channel 1", change "channel 2" to "channel 1"
Choose an ouput directory and click "add to queue" then "encode"
Should take under a minute.

Remember to change "channel order mode" back to "disabled" afterwards or it will do the same the next time you use it.

[twogurusindrag]

Use https://xmedia-recode.de/en/

Set format to "matroska"
Set video mode to "copy"
Set audio mode to "convert" and choose codec "flac"
Under audio tab "channel mapping" set "channel order mode" to "custom" , leave "channel 1" as "channel 1", change "channel 2" to "channel 1"
Choose an ouput directory and click "add to queue" then "encode"
Should take under a minute.

Remember to change "channel order mode" back to "disabled" afterwards or it will do the same the next time you use it.

Worked like a charm. Thanks!