Comment 102 for bug 602934

(In reply to comment #88)
> Tried v12 on win 7 x64 so far. Main finding so far is that exported bit rates
> are not correct. Exporting a stereo music track, both with FFmpeg 0.5 and 0.6
> and according to Medianfo and iTunes,
>
> 24 kbps exports as 60 kbps
>
> 96 and 256 kbps both export as 150 kbps (the exported files are the same size).

Yep, I noticed that too. But, the ffmpeg command does the same thing:

From WAV to M4A at 256kbps...

llama:~$ /usr/local/lib/audacity/ffmpeg -i 1.wav -ab 256k 2.m4a

<snip>

[wav @ 0x1009810]max_analyze_duration reached
[wav @ 0x1009810]Estimating duration from bitrate, this may be inaccurate
Input #0, wav, from '1.wav':
  Duration: 00:00:30.00, bitrate: 705 kb/s
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 1 channels, s16, 705 kb/s
Output #0, ipod, to '2.m4a':
  Metadata:
    encoder : Lavf52.64.2
    Stream #0.0: Audio: libfaac, 44100 Hz, 1 channels, s16, 256 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
size= 238kB time=29.93 bitrate= 65.2kbits/s
video:0kB audio:228kB global headers:0kB muxing overhead 4.718516%

And from that M4A back to WAV...

llama:~$ /usr/local/lib/audacity/ffmpeg -i 2.m4a -ab 256k 2.wav

<snip>

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '2.m4a':
  Metadata:
    major_brand : M4A
    minor_version : 512
    compatible_brands: isomiso2
    encoder : Lavf52.64.2
  Duration: 00:00:29.93, start: 0.000000, bitrate: 65 kb/s
    Stream #0.0(und): Audio: libfaad, 44100 Hz, 2 channels, s16, 62 kb/s
Output #0, wav, to '2.wav':
  Metadata:
    encoder : Lavf52.64.2
    Stream #0.0(und): Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
size= 5152kB time=29.91 bitrate=1411.2kbits/s
video:0kB audio:5152kB global headers:0kB muxing overhead 0.000834%

Notice how even though I specified 256kbps when I converted to M4A, it actually
wound up being 62kbps.