CODEWITHSUNDEEP
dockermlt
seawolf
seawolf

Reputation: 2195

Can't get MLT Framework to process audio in Docker container

I am using Docker to create a container for video processing using the melt command. All videos output at the moment do not include any audio.

Here's the Dockerfile:

FROM ubuntu
RUN apt-get update
RUN apt-get install -y melt swh-plugins
WORKDIR /input
CMD [ "melt", "input.mp4", "-consumer", "avformat:/output/output.mp4" ]

When I run the container, I get the following error:

consumer_avformat.c: Unable to encode audio - disabling audio output.

I suspect this tells you a lot. However, I have tried running the command as:

melt input.mp4 -consumer avformat:/output/output.mp4 acodec=libmp3lame

... when I do, I do not get the error, but there is still no audio in the output file.

Because I don't really understand audio processing, I'm not sure if I'm missing plugins or somehow otherwise not specifying a requirement. Should be a relatively easy fix for someone who knows their way around Docker and multimedia.

Upvotes: 0

Views: 360

Answers (2)

seawolf
seawolf

Reputation: 2195

It turns out that I needed to install the ubuntu-restricted-extras package to my Dockerfile. Once that was in place, everything works as expected.

Upvotes: 1

Dan Dennedy
Dan Dennedy

Reputation: 481

In the first instance, audio output is probably defaulting to aac, but in most versions of libavcodec, aac requires that you also say "strict=experimental". If you explicitly set acodec=aac, then melt automatically adds that for you. Soon, libavcodec aac encoder will exit experimental state (if it has not already in recent days). In general, you are under-specifying encoding parameters.

In the second instance, how do you know there is no audio? Quicktime does not support MP3 in MP4, and maybe also some other media players.

Upvotes: 1

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