[FFmpeg-user] How to copy MP3 320 bps frames?

[Ulf Zibis]

Hi,

when i use the lame encoder to transcode a 320 bps mp3 to VBR, I can see, that some percentage of frames is encoded to 320 bps frames, so these frames seem to contain important data  :

$ lame -V1 in.mp3 out.mp3
LAME 3.100 64bits (http://lame.sf.net)
Using polyphase lowpass filter, transition band: 19383 Hz - 19916 Hz
Encoding in.mp3 to out.mp3
Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=1)
     Frame          |  CPU time/estim | REAL time/estim | play/CPU |    ETA
  10104/10104 (100%)|    0:04/    0:04|    0:04/    0:04| 54.411x|    0:00
  32 [   29] *
  40 [    0]
  48 [    0]
  56 [    0]
  64 [    0]
  80 [    0]
  96 [    0]
112 [    2] %
128 [    0]
160 [    0]
192 [ 2473] %%%%%%%%%%%%%%%%%%%%%%%%%%%%*
224 [ 5892] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
256 [ 1506] %%%%%%%%%%%%%%%%%*
320 [  202] %%%
-------------------------------------------------------------------------------
    kbps        LR    MS  %     long switch short %
   222.3       98.3   1.7        95.7   2.3   2.0
Writing LAME Tag...done
ReplayGain: +2.1dB


Would it be possible to just copy those frames using ffmpeg, instead of re-encoding them to get the maximum of quality?

-Ulf