2 Replies Latest reply on Apr 17, 2012 10:21 AM by martinpat1

    AVCHD bit rates - what's going on?!

    martinpat1 Level 1

      Very confused!!!


      I record video using my SONY camera using the FH setting at 17 MB. When I import the video, select the clip in Project and view Properties, Elements reports that it's 2.7 MB / second. When I render the video as an MP4 file and set the bitrate to 17 MB, the video produced is indeed 17 MB (checked using other media sofware), but when I import this into Elements and click on Properties, it states again it's 2.7 MB. Why?


      If I export the video as an M2T file, it doesn't matter what bitrate I use, the final file size is always the same (much bigger than the original file size), even though the estimated file size changes as I change the bitrate setting. Also, the reported bitrate is 3.7 MB / second, even though the original file is 2.7 MB!


      Is there a difference between the quality of the rendered video if MP4 is selected instead of M2T, and what's the difference as they both use H264?



        • 1. Re: AVCHD bit rates - what's going on?!
          Steve Grisetti Adobe Community Professional

          Well, there are many brands of H.264 codec (Sony, Apple, Main Concept, etc.) and no two programs compose event the same brand of codec file exactly the same way. So no program is going to give you the exact same size file out as you put in.


          Composition can also affect file size. Video with little action or changing scene can create a much smaller file than video with a lot of action.


          M2Ts are generally of the highest quality, since they're generally used for editing and creating BluRay discs. While MP4s are generally used for online display or playback on portable devices.


          I know that's not a satisfying answer -- but if you can find someone who can show mathematically why every program creates the size of files they create and how to predict what size file a program will create, I'd love to meet him. Though even after a decade of working with digital video, I'd probably still have no idea what he was talking about.

          • 2. Re: AVCHD bit rates - what's going on?!
            martinpat1 Level 1

            Thanks Steve


            It's just so weird how the file size is the same regardless of the bitrate - but only when exporting as m2t. And how can Elements tell me the bitrate is 2.7 MB (so massively different from 17 MB) when every other bit of software tells me otherwise!! I feel like it's my lack of technical knowledge that's the problem, but I'm not convinced it is...