[Question] Encoding with --he and specifying bitrate

fortin-mo commented 5 years ago

I was wondering if you could specify a desired bitrate when using he-encoder. It looks like it always pick 192kbs for 6 channels audio. I thought would only do that when using 0 ( --cvbr 0, --abr 0, etc. )

INPUT MEDIA INFO

Format : PCM 
Format settings : Little / Signed 
Codec ID : 00000001-0000-0010-8000-00AA00389B71 
Duration : 1 h 0 min 
Bit rate mode : Constant 
Bit rate : 4 608 kb/s 
Channel(s) : 6 channels 
Channel positions : Front: L C R, Back: L R, LFE 
Sampling rate : 48.0 kHz 
Bit depth : 16 bits 
Stream size : 1.94 GiB (100%) 

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COMMAND LINE

qaac64.exe --cvbr 224 --he --quality 2 --no-optimize --threading --ignorelength audio.wav -o audio.m4a

qaac 2.68, CoreAudioToolbox 7.10.9.0

audio.m4a
AAC-HE Encoder, CVBR 192kbps, Quality 96
0:51.840 (2.8x)

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OUTPUT MEDIA INFO

Format : MPEG-4 
Format profile : Apple audio with iTunes info 
Codec ID : M4A (M4A /mp42/isom) 
File size : 87.1 MiB 
Duration : 1 h 0 min 
Overall bit rate mode : Variable 
Overall bit rate : 202 kb/s 
Encoded date : UTC 2019-01-31 00:42:54 
Tagged date : UTC 2019-01-31 00:46:21 
Writing application : qaac 2.68, CoreAudioToolbox 7.10.9.0, AAC-HE Encoder, CVBR 192kbps, Quality 96 
Encoding Params : (Binary) 

Audio 
ID : 1 
Format : AAC 
Format/Info : Advanced Audio Codec 
Format profile : HE-AAC / LC 
Format settings : Explicit 
Codec ID : mp4a-40-2 
Duration : 1 h 0 min 
Bit rate mode : Variable 
Bit rate : 201 kb/s 
Maximum bit rate : 341 kb/s 
Channel(s) : 6 channels 
Channel positions : Front: L C R, Side: L R, LFE 
Sampling rate : 48.0 kHz / 24.0 kHz 
Frame rate : 23.438 FPS (1024 SPF) 
Compression mode : Lossy 
Stream size : 86.7 MiB (100%) 
Encoded date : UTC 2019-01-31 00:42:54 
Tagged date : UTC 2019-01-31 00:46:21

As you can see, even though I specified --cvbr 224 expecting an average bitrate of 224kbs, it picked 192 ( quality 96 ).

nu774 commented 5 years ago

Apple AAC encoder supports only limited set of bitrate configuration, and 192kbps is the highest for HE/48000Hz/5.1ch. Run qaac --formats to see supported format/bitrate table.

fortin-mo commented 5 years ago

👍 thanks

sergeevabc commented 4 months ago

Why did you use --no-optimize?

nu774 / qaac

[Question] Encoding with --he and specifying bitrate #57