This is not strictly a plex question but does have a plex slant on it. Lets take an example. I have an video which has the following audio profile. You can see the bit rate mode is constant. Audio ID : 2 Format : E-AC-3 JOC …

I use 224 kbps for AAC myself. It is the “sweet spot” for me, providing high quality audio without taking too much of storage space. If you are downmixing from surround sound, you want to normalize the loudness of the downmixed signal. Otherwise the result is usually too quiet. I am using XMedia R…

Lossy compression pretty much always produces variable bitrates. Even the classic mp3 constant bitrate is just a stream with variable bitrate, which has been “stuffed” with filler bits which don’t do anything for the sound reproduction. (That’s why you can later remove the filler and get back a vari…

Thanks, informative as ever, much appreciated. [image] OttoKerner: Lossy compression pretty much always produces variable bitrates. I’ve never experienced this and I’ve down mixed a fairly large amount of media over the years. However, up until recently I’ve used handbrake (setting below)… …

Thanks. I do two pass encoding on the video stream anyhow so doing the analysis would not be a problem for audio. Thanks again.

A brief update on this topic. After some more investigation I’ve discovered that when down mixing to stereo using aac that there can be some drift with the bit rate which is why it then gets reported as variable even when the constant bit rate is passed -ab 256k. This is not audio drift but bit ra…

The FDK library is recommended anyway, due to its superior sound quality. It’s just no longer included by default due to license issues.

[image] OttoKerner: The FDK library is recommended anyway, due to its superior sound quality. Thanks. I’ll continue to use that going forward. It does bring up one follow on question. As I’m on linux I need to compile from source ffmpeg to include this encoder. That’s no problem but I’m w…

Audio Down mixing to stereo sometimes results in variable bit rate

General Discussions

anon5074910 July 10, 2023, 8:29pm 9

May have found an answer to this. Assuming this Version of FFMPEG in Plex - #2 by anon18523487 is still true then it appears plex uses it’s own custom ffmpeg itself so anything I configure myself should be independent of that.

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Audio Down mixing to stereo sometimes results in variable bit rate

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