0 Replies Latest reply on Jul 31, 2013 8:08 PM by Guy Burns

    Exporting stills: VBR vs CBR

    Guy Burns Level 1

      I've been experimenting with various export modes from Premiere to compare quality, encode time, and file size. Most of my projects involve a lot of dissolving stills, and I expected funny things to happen. And they have.


      Most of the info I've been able to dig up about CBR and VBR for video seems to suggest that file size, when the Target and Max bit rates are the same, should be similar for CBR, VBR 1-pass, and VBR 2-pass. Sounded reasonable to me, but it is certainly not the case for dissolving stills.


      My test sequence was a 1920 x 1080 still, 10 seconds, with a 3-second fade to blackness at each end. Figures in brackets are the bit rate, Target/Max. Export was not multiplexed so I ended up with .xmpses files as well as the .m4v files.


      Test Results


      CBR (35):          9 seconds, 43 MB.


      1-Pass (35/35): 9 seconds, 18 MB

      1-Pass (25/35): 9 seconds, 18 MB


      2-Pass (35/35): 15 seconds, 6.7 MB

      2-Pass (30/35): 15 seconds, 6.7 MB

      2-Pass (25/35): 15 seconds, 6.7 MB




      No choice really. Use 2-Pass. Why is there such a huge difference in file size?



      XMPSES files

      Another reason I'm experimenting is to find out which files types exported out of Premiere will not need transcoding when sent to Encore. I've worked that out, but I get these .xmpses files as well as video and audio.


      Q1. Are these xmpses files needed when I import them into Encore or can I safely delete them?


      Q2. Quicktime, VLC, MPEG Streamclip can't open the exported .m4v files. Which suprised me, given that VLC and MPEG Streamclip can usually open almost anything. But Premiere and Encore will import the files. Why is that?


      Q3. Assuming I had a proper video file which I exported to video, audio and xmpses files, what program could I use to re-multiplex the video and audio without transcoding? Would the xmpses file be needed to do that?