[FFmpeg-user] ffmpeg audio encoding

Simon Medved simon at medved.in
Wed Oct 21 10:42:34 EEST 2020


i have a question what is the recommended way for transcoding only audio
and keep video as is.

I tried this with command:
ffmpeg -n -i something.mkv something_else.mkv -map 0 -vcodec copy -scodec
copy -acodec ac3 -b:a 640k

The thing is that using this command with a 10+GB file the process is very
very slow and it would take more than 1 day.

I tried manual to remove audio from mkv, encode it in ac3 and repack it
back which was done in an h.

Do you have any idea what can be improved?

File i was using:
<Stream id="48782" streamType="1" default="1" codec="hevc" index="0"
bitrate="48081" bitDepth="10" chromaSubsampling="4:2:0" codedHeight="2160"
codedWidth="3840" colorPrimaries="bt2020" colorRange="tv"
colorSpace="bt2020nc" colorTrc="smpte2084" frameRate="23.976" height="2160"
level="153" profile="main 10" refFrames="1"
displayTitle="4K (HEVC Main 10 HDR)"
HEVC Main 10 HDR)"/>

<Stream id="48831" streamType="2" codec="dca" index="3" channels="6"
bitrate="1536" language="English" languageCode="eng"
audioChannelLayout="5.1(side)" bitDepth="16" profile="ma"
samplingRate="48000" title="[ORIGINAL] DTS-HD MA 5.1 @ 2238 kbps"
displayTitle="English (DTS-HD MA 5.1)" extendedDisplayTitle="[ORIGINAL]
DTS-HD MA 5.1 @ 2238 kbps (English)"/>

Thank you.

*Lep pozdrav // Best regards,*
Simon Medved

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