5 Replies Latest reply on Nov 14, 2012 4:57 PM by Howard Hoffman

    Adobe Media Encoder does not honor VBR target rate

    Howard Hoffman Level 1

      CS6

       

      H.264 VBR 2-pass video.  AC3 audio.  Multiplexer on

       

      Targetted 18 Mbps.  Ended up close to 35 Mbps.  Audio is corect.

       

      The issue only appears when multiplexer is on.

       

      When multiplexer is off, the file size and bit rate looks normal:

      Bit rate mode                : Variable
      Maximum bit rate             : 35.0 Mbps

       

      When multiplexer is on, the file size matches 35 Mbps.  Note the extra "bit rate" line

      Bit rate mode                : Variable
      Bit rate                     : 34.1 Mbps
      Maximum bit rate             : 35.0 Mbps

       

      Same thing goes for MPEG2-DVD

       

      MPEG2-DVD VBR 2-pass video. AC3 audio. Multiplexer on, variable bitrate

       

      Targetted 3.7 Mbps.  Ended up around 4.3 Mbps.

       

      The issue again is only when multiplexer is on.

       

      When multiplexer is off, the file size and bit rate looks normal:

      Bit rate mode                : Variable
      Bit rate                     : 3 586 Kbps
      Nominal bit rate             : 9 000 Kbps

       

      When multiplexer is on, the file size matches 35 Mbps.

      Bit rate mode                : Variable
      Bit rate                     : 4 343 Kbps
      Nominal bit rate             : 9 000 Kbps

       

      Is this a feature or bug?  I vaguely rememer this was mentioned before but can't find the thread.

       

      Thanks