Author Topic: How to configure mp3 audio output-only?  (Read 356 times)

pstein

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How to configure mp3 audio output-only?
« on: June 03, 2018, 05:02:04 PM »
Assume I drag an *.mp4 or *.mkv video file onto Avidemux and want to extract the audio part only.

Therefore I set on the left side Audio Output to

MP3 (lame)

When I click on the "Configure" button then I set the Bitrate mode to ABR which means variable bitrate AFAIK.
Surprisingly  for the bitrate value itself only one value can specifed (e.g. 160). I though when a variable bitrate is taken then an upper and lower bitrate value should be necessary.

Furthermore I wonder about the meaning of "quality". Do smaller values mean poorer quality or the opposite?

At last I found a checkbox "Disable reservoir".

What does this mean?

Thank you
Peter

Jan Gruuthuse

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Re: How to configure mp3 audio output-only?
« Reply #1 on: June 03, 2018, 05:46:45 PM »
Best you install audacity with drag and drop support (if you are on windows). This way you have a greater control on exporting mp3 from audacity.
- https://www.audacityteam.org/
- https://www.audacityteam.org/download/windows/
-- FFmpeg import/export library – Allows Audacity to import and export many additional audio formats such as AC3, AMR(NB), M4A and WMA, and to import audio from video files.
-- LAME MP3 encoder – Allows Audacity to export MP3 files

- ABR bitrate goes here up to 320 in avidemux
- -q 0:  Highest quality, very slow
- The term bit reservoir is used exclusively in the MP3 specification.

« Last Edit: June 03, 2018, 05:50:21 PM by Jan Gruuthuse »

eumagga0x2a

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Re: How to configure mp3 audio output-only?
« Reply #2 on: June 03, 2018, 09:56:13 PM »
Assume I drag an *.mp4 or *.mkv video file onto Avidemux and want to extract the audio part only. Therefore I set on the left side Audio Output to MP3 (lame)

Depending on the audio format in the video and the capabilities of the targeted audio player, you may want to use copy mode to dump the audio stream without re-encoding.

Quote
When I click on the "Configure" button then I set the Bitrate mode to ABR which means variable bitrate AFAIK. Surprisingly for the bitrate value itself only one value can specifed (e.g. 160). I though when a variable bitrate is taken then an upper and lower bitrate value should be necessary.

Avidemux uses the lame_set_preset call of the LAME API which accepts only one parameter for bitrate – the average bitrate itself. The API offers also more fine-grained settings (lame_set_VBR_mean_bitrate_kbps, lame_set_VBR_min_bitrate_kbps, lame_set_VBR_max_bitrate_kbps and lame_set_VBR_hard_min), but I am not sure it is worth the effort to implement it in Avidemux while specialized software exists which is better at this.

pstein

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Re: How to configure mp3 audio output-only?
« Reply #3 on: June 04, 2018, 04:22:12 AM »
Ok, thank you.

Just a remark to the "quality" value:

As I found out the resulting *.mp3 with quality=0 is only a few bytes bigger than for quality=2.
Similarly the encoding time is only a few seconds longer.

So why not always automatically  selecting quality=0?