How to Compare Two Lossless Audio Files on Linux

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I have an M4A file which is also converted to a FLAC file. I'd like to see if the conversion is lossless, namely, whether the output to pcm from M4A is exactly identical to the one from FLAC decoding.

I assume there's a way to use FFmpeg or Libav to produce some "raw" output and compare them?

Best Answer

I'd try converting them both to WAV and comparing their checksums.

ffmpeg -i file1.m4a file1.wav
ffmpeg -i file2.flac file2.wav
md5sum file1.wav
md5sum file2.wav
rm file?.wav

Compare the md5s produced. If they match, congratulations! Your files contain the same data. If they don't match, post the output of those commands here, and I'll look. Potentially there is a bitrate difference or something (there ought not to be... but there may be, I don't know.)

Note that the ffmpegs will generate comparatively large intermediate files.

Related Solutions

Converting RGB images into lossless video with avconv / ffmpeg

With the help of a ffmpeg contributor it was found out that both ffmpeg and libav create flawless lossless Quicktime files. The problem seems to be the graphic card driver displaying the videos wrongly (since GStream based players and VLC both display it wrongly, however VLC is exporting perfect PNGs of video frames). If you want to check if a video is really containing the frames pixel by pixel, try using

$ ffmpeg -i input.png -vcodec qtrle out.mov

$ ffmpeg -i input.png -f framecrc -
$ ffmpeg -i out.mov -f framecrc -

This will output frame data checksums.

For a visual comparison, convert the lossless video back to single frames and compare those.

Lossless concatenation of ogg vorbis files

ffmpeg -i "concat:ogg1.ogg|ogg2.ogg|ogg3.ogg" -c copy out.ogg creates a concatenated ogg file on my system, just a little bit smaller than the separate files combined (probably because of the shared metadata). It sounds the same to me, so the concatenation should be lossless. However, this doesn't add a small gap between the files.

ffmpeg -f concat -safe 0 -i ogg1.ogg -i ogg2.ogg -c copy out.ogg is supposed to work but it gives this error on my Homebrew (macOS) ffmpeg as of 3.3.2.

[concat @ 0x7f91e8800400] Line 1: unknown keyword 'OggS'
ogg1.ogg: Invalid data found when processing input

Source: https://trac.ffmpeg.org/wiki/Concatenate

Best Answer

Related Solutions

Converting RGB images into lossless video with avconv / ffmpeg

Lossless concatenation of ogg vorbis files

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