Caveats when using ‘avidemux’ (under Linux).

One of the applications available under Linux, that can help edit video / audio streams, and that has been popular for many years – if not decades – is called ‘avidemux’. But in recent years the subject has become questionable, of whether this GUI- and command-line- based application is still useful.

One of the rather opaque questions surrounding its main use, is simply highlighted in The official usage WiKi for Avidemux. The task can befall a Linux user, that he either wants to split off the audio track from a video / audio stream, or that he wants to give the stream a new audio track. What the user is expected to do is to navigate to the Menu entries ‘Audio -> Save Audio’, or to ‘Audio -> Select Track’, respectively.

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What makes the usage of the GUI not straightforward is what the manual entries next state, and what my personal experiments confirm:

  • External Audio can only be added from ‘AC3′, ‘MP3′, or ‘WAV’ streams by default,
  • The audio track that gets Saved cannot be played back, if In the format of an ‘OGG Vorbis’, an ‘OGG Opus’, or an ‘AAC’ track, as such exported audio tracks lack any header information, which playback apps would need, to be able to play them. In those cases specifically, only the raw bit-stream is saved.

The first problem with this sort of application is that the user needs to perform a memorization exercise, about which non-matching formats he may or may not, Export To or Import From. I don’t like to have to memorize meaningless details, about every GUI-application I have, and in this case the details can only be read through detailed research on the Web. They are not hinted at anywhere within the application.

(Updated 3/23/2019, 15h35 … )

Continue reading Caveats when using ‘avidemux’ (under Linux).

Identifying the container-file-format, separately from the Codec.

One of the facts which the public is well-aware of, is that Sound and Video are usually distributed in compressed form, through the use of a ‘Codec’, which stands for ‘Compressor / Decompressor’. What may still have some people confused though, is that there is a separate distinction in file-formats, which is the ‘Container File Format‘. The latter distinction is observed, when giving the file its filename-suffix, such as .MP3, .MPEG, .MP4, .OGG, .M4A, etc..

  • An .MP3-File will contain sound, compressed with the Codec: MPEG-2, Layer III
  • An .MPEG-File will contain video and sound, compressed with the Codecs: MPEG-2 or MPEG-1, And AC3 or MPEG, Layer III Audio (Hence, ‘MP3 Audio’ is allowed.)
  • An .MP4-File will contain video and sound, compressed with the Codecs: H.264 or MPEG-4, And AAC
  • An .OGG-File will mostly contain video and / or sound, compressed with the Codecs: Theora (video) And Vorbis (sound)

Finally, because the ‘AAC’ Sound Codec, which stands for ‘Advanced Audio Codec’, has qualities which have been found desirable outside its initial usage-scenario, for movie-making, just for Audio, there has been some possible confusion, as to how the users should name a container file, which contains only AAC-compressed audio, but no video. On my Linux-computers, I’m used to giving those files the filename-suffix ‘.M4A’ . Other people may at one time have been doing the same thing. But because the suffix was not widely recognized, Apple specifically, may have just started the trend, of just naming the container files ‘.MP4-Files’ again, even though they contain no video. This may simply have helped their customers understand the file-formats better.

The AC3 and AAC sound Codecs both offer directionality in the sound, which was useful for movies, but which will exceed the degree of directionality, that ‘MP3 Audio’ offers. And so, even though AAC offers small file-sizes, it has become popular for Music as well, because the way in which the Advanced Audio Codec compresses its sound is ‘so smart’, that listeners tend to hear very high-quality sound anyway.

Dirk