[FFmpeg-user] Opus : difference between .opus and .ogg file extension

Carl Eugen Hoyos ceffmpeg at gmail.com
Thu Nov 30 14:18:17 EET 2017

2017-11-30 13:14 GMT+01:00 Carl Eugen Hoyos <ceffmpeg at gmail.com>:
> 2017-11-30 11:24 GMT+01:00  <nerbrume at free.fr>:
>> I'm encoding my audio files to opus, with the following command:
>>> ffmpeg -i test.mp3 -acodec libopus -b:a 64000 -vbr on test.opus

>> However, encoding my file with an ogg extension :
>>> ffmpeg -i test.mp3 -acodec libopus -b:a 64000 -vbr on test.ogg
>> produces a different file from the previous one (md5 are mismatched).
> Use -fflags +bitexact to get identical files, you will also get different
> files when writing to out1.ogg and out2.ogg.

To elaborate:
The ogg files contain a serial number if the option is not specified,
this serial number is created with a function producing pseudo-random

Carl Eugen

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