5 Replies Latest reply on Jul 11, 2011 11:51 PM by Jim_Simon

    Problems trimming MTS files?

    Sengstack Level 1

      An editor, who works with Final Cut Pro, made the following statement:

       

      "I personally  wouldn't edit an MTS file; although Premiere can handle it. It's  not really an editing format, which is why it has problems when  trimming. It's a smartly compressed capture format that is usually  transferred into a different spec for editing."

       

      My take is that it's a good thing P Pro handles MTS (AVCHD) files  natively. It significantly speeds up the workflow. And I have not  noticed any trimming issues. But this comment raises a red flag.

       

      Does anyone care to weigh-in on this?

       

      Jeff Sengstack

        • 1. Re: Problems trimming MTS files?
          Jim_Simon Level 8

          If you don't want to edit AVCHD, then just don't shoot AVCHD.

           

          It sounds to me like the editor who made that comment is trying to justify FCP's lack of native media handling, as if it were a good thing somehow.  But the reality is, for those editors who'd rather not edit interframe media, they can always convert it before editing.  But with FCP, those editors who don't care that much and want to edit natively are out of luck.  They're stuck with the conversion whether or not they want it.

           

          And that's not a good thing.

          • 2. Re: Problems trimming MTS files?
            Sengstack Level 1

            Well put Jim.

             

            But I'm still wondering about trimming accuracy. I have not noticed any

            issues with making frame-accurate trims. I just clicked through some

            AVCHD footage, one frame at a time, and each frame was a discrete image.

            Does P Pro compensate for interframe media? For example, does it

            interpolate frames?

            • 3. Re: Problems trimming MTS files?
              Colin Brougham Level 6
              I have not noticed any issues with making frame-accurate trims. I just clicked through some AVCHD footage, one frame at a time, and each frame was a discrete image. Does P Pro compensate for interframe media? For example, does it interpolate frames?

               

              Yes, of course--FCP does the same thing, only it's "baking" it into the L&T files using whatever I-frame codec you select, e.g. ProRes. AVCHD uses long GOP encoding, so you've got discrete frames only every so often, with bits and pieces of predicted frames in between. In a shot that doesn't change much, there aren't many differences to encode, so you can have "frames" that really don't consist of much video data. The MPEG decoder knows to look forward and backward from those predicted frames to the independently-coded frames, and uses those as references to build the frames in between. Premiere Pro is doing this on the fly--that's why you need a fairly brawny PC to play back AVCHD in full-resolution, and it's also why you might have noticed some pretty nasty break-up if you don't set your Program Monitor Playback Resolution to Full. When it's at Full, both the independent frames and the predicted frames are decoded and displayed; when it's anything less than Full, not only does Premiere Pro drop the resolution, but it also doesn't decode all the predicted frames. It takes much less horsepower, but it can be pretty jarring and nearly impossible to edit, at least from a visual standpoint.

               

              You can step through frame-by-frame and see a whole, discrete image because Premiere Pro is doing the decoding for each of those previewed frames--that's a lot easier than doing it at full speed. From a timebase standpoint, it doesn't really matter if there is encoded video data there or not; it's a "frame" in the video sense, and you can edit on those frame demarcations. Now, since Premiere Pro doesn't do "smart encoding," it doesn't matter whether you edit on a GOP boundary or somewhere in between, all frames will be re-encoded on export. That's no big deal, though; with FCP, you're transcoding twice.

               

              Now, go tell your friend he's being silly and he should come join us

              1 person found this helpful
              • 4. Re: Problems trimming MTS files?
                Sengstack Level 1

                Colin, thanks for the explanation. I'll try to let my friend down easy.

                • 5. Re: Problems trimming MTS files?
                  Jim_Simon Level 8
                  I have not noticed any issues with making frame-accurate trims.

                   

                  I should hope not.  PP is, after all, an NLE.  It'd be pretty useless if it couldn't do things at a frame accurate level.