Avidemux sees 48kHz sample rate AAC audio in FLV container as 44.1kHz

[eumagga0x2a]

To get a nice testcase, use e.g. https://www.youtube.com/watch?v=HhiVuIRw4tM (Berlin Phil. promo with Pavane by Fauré), format code 18 is enough, then convert 44100 audio to 48000 while changing the container to FLV:

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ffmpeg -i source.mp4 -c:v copy -c:a aac -b:a 96k -ar 48000 flv-with-48k-audio.flv

Load flv-with-48k-audio.flv in Avidemux and check the properties of the video and audio: Avidemux identifies the audio sample rate as being 44100 Hz. When played in Avidemux, the audio is half tone lower in pitch than when played in ffplay and exhibits crackling noise and interruptions, confirming that Avidemux really insists on 44.1k for audio (FLV container limitation) instead of listening to faad, which repeatedly complains that

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[initFaad]  [FAAD]Frequency mismatch!!! 44100 to 48000 (SBR ?)

Extracting the audio from the sample and loading it as an external audio file allows perfect playback in Avidemux.

This is an old and probably not really important issue, just wanted to have it reported. The whole is very similar to https://trac.videolan.org/vlc/ticket/13837. That bug report cites from Adobe specs that a player should ignore 44100 sample rate in such cases.

(edit: modified the subject to use correct units)