I'm trying to transcode to 2.0 AAC at 192 kbps (all channels together should = 192 kbps).

ffmpeg -i "$file" -map 0:a:m:language:eng -vn -acodec copy -f nut - | ffmpeg -f nut -i - -c:a aac -b:a 128k -ac 2 "${file%.mkv}".eng.aac

But looking at my output I see it sometimes go as high as 300 kbps?

And mediainfo also reports the .aac file created is variable bitrate. But calculating time x bitrate the file has the expected

Meanwhile ffmpeg says that the native encoder should not be used with VBR because that would be less quality than constant bitrate.

Output while encoding it goes up to 300 kbps then drops to ~100kbps :

size=    6239kB time=00:02:12.88 bitrate= 384.6kbits/s speed=87.3x

It seems to be displaying the bitrate of the input, and not the output, when converting DTS I see bitrates of like ~3000 kbits/s there

Is this behavior expected?

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.