[Libav-user] encoding bitrate wrong

[mattes]

I ported an older mp4 encoder application (using ffmpeg 0.4.9 libs)
 over to the ffmpeg 0.7.11 (on Fedora15).
Encoding is working, but there is one minor glitch.

   Bitrate is set via AVContext->bit_rate = bitrate.

The encoding bitrate is either very low or very high.
  e.g. I try 500kbits or 2500, I end up with an encoding bitrate of >6000.
     when I set it to 1500, i'll get 187kbits.

The code was using some deprecated functions, which i subsequentely switched over
to the newer API calls.

  avcodec_alloc_context();           ==> avcodec_alloc_context3(codec)
  avcodec_open(m_avctx, m_codec)      ==> avcodec_open2(m_avctx, m_codec, NULL)

But no change in behaviour.

Is bitrate configuration done different these days with 0.7.x or later?
What am I missing?