7 Replies Latest reply: Apr 10, 2010 7:59 PM by Alan McDonley
Alan McDonley Level 1 Level 1 (0 points)
I learned that I can repackage my AVCHD "lite" footage (.m2ts container) with

ffmpeg -i myvideo.m2ts -acodec copy -vcodec copy myvideo.m4v,

into an .m4v container which iMovie will import. Infact, the import does not transcode into AIC so the file size stays the same.

This is good, no?

iMac Core i5 27", Mac OS X (10.6.2)
  • Alan McDonley Level 1 Level 1 (0 points)
    If I understand what I am reading... Steve Mullen in "The Ins and Outs of iMovie 09" recommends using Handbrake to convert .m2ts AVCHD to .m4v, (then suggests to rename .m4v to .mp4) for import to iMovie, so it seems I'm on the right path with repackaging to .m4v/.mp4 container to import AVCHD "lite" from Panasonic ZS3/TZ7 camera footage that I didn't save as an SD card archive.

    (For those not familiar with this "lite" thing - Panasonic frame doubles 1280x720p. iMovie will import it from the camera or a camera archive on SD card, but if you imported to a PC, then moved to a Mac, all you have is .m2ts files which iMovie will not import.)

    So answer is yes - importing .m4v/.mp4 is good.
  • AppleMan1958 Level 7 Level 7 (27,385 points)
    This is OK if you have a very fast Mac and a short movie (or a low resolution movie)

    h.264 is a delivery codec, and highly compressed. There is one full frame for about every 24 frames of video. The rest are highly compressed by containing info only about what has changed since the prior frame, direction of motion, etc.

    If you convert to AIC, every frame is converted to a full frame, so editing is much faster.

    Also, a Project in iMovie is basically a set of instructions that is executed against the event file when the project is rendered. If the Event is compressed (like h.264), the Mac has to resolve all the partial frames into full frames, and do all the other threads to produce the movie at render time. It is virtually impossible to do speed changes without converting everything to full frames, except on the lowest resolutions. You will also run out of virtual memory much faster if using h.264 at high resolutions.

    When you convert to AIC, your event will become 8 to 10X larger, because the partial frames are converted to full frames.
  • Steve Mullen Level 2 Level 2 (250 points)
    H.264 -- is a codec. Codecs are codecs. Sometimes we acquire and sometimes we distribute video.

    The important thing to understand is that from the point of view of tVIDEO, nothing is ever made better by converting it to another codec. Quality is only lost!

    In the case of h.294 or AVCHD to AIC, the files only get many times large and your disk has to be many times faster. This is a huge negative for anyone using a laptop.

    Therefore, it always best to edit natively.

    But what about the real frames and the non-real frames. Pure myth! As each frame it decoded it has exactly the same quality as any other frames. (The fact the data packets, which are invisible to any human, vary in size is not relevant. In order to work with ANY frame it is decompressed to uncompressed RGB video.

    But doesn't that mean your disk has to work harder. Nope. Huge blocks of data are read into memory. The decompressor keeps several GOPS of data in RAM. It simply works with the data packets it needs to generate the RGB frames YOU see.

    The claim is that this takes too much time. If that were true, how does my iPhone and now my iPad play 720p30 H.264 video?

    The answer is frame-size and frame-rate and number of streams. There are certainly many with Macs that are so slow they need the speed advantage of AIC. But, most newer systems can play 720p30. And, with very recent Macs you can likely play 1080i60.

    However, when you perform a dissolve you need two streams of video. Here's where a QUAD CORE is needed.

    So the question is how smoothly do your H.264 source files play? And, does it really matter during editing? (To me it does not matter.) Only, if you can NOT stand how things work should you take the LONG TIME it takes to convert to AIC. So it's not the length of your movie that's the issue. It's how many hours of source material do you have?

    PS: there is another reason you might want to convert to AIC via Optimize. For most people 960x540 is good enough. Now you cut the amount of disk space needed by your AIC by 1/4!
  • Alan McDonley Level 1 Level 1 (0 points)
    I bought the Intel based i5 quad core iMac specifically with AVCHD editing in mind, although I have read that iMovie only uses two cores max.

    I am not in a hurry when rendering. On my previous platform (2.4GHz Intel P4 with only 2GB ram with H.264 hardware codec display card) I always launched the render before heading off to bed at night. I only view the rendered videos on my TV using pyTivo->(transcoded with ffmpeg)->Tivo which sadly is only MPEG2. I have tried Toasting my 720p to an AVCHD DVD to my Blu-Ray player and it seemed to be the same as the MPEG2 transcoded Tivo version. Since I am not doing "Full HD" life may be less complex.

    My big concern with non-AIC editing was if iMovie would allow exact frame editing. (Pinnacle Studio 12 on the PC was confused by Panasonic's frame doubled AVCHD "Lite" and would jump three second increments when selecting a split or in/out point.) Most of the good editors I have used prior to moving to the Mac, used proxy editing on a lower res i-framed copy. Based on Steve Mullen's comments here and in "The Ins and Outs of iMovie 09" I am starting to feel comfortable that iMovie 09 is going to handle my 720p AVCHD "lite" footage fine.
  • hatetea58 Level 1 Level 1 (0 points)
    first, which version of imovie do u use. Only imovie 08 and 09 can support avchd files. Addtionally, h.264 codec also cant be accepted by imovie. dv and mpeg codec are proper.
  • Alan McDonley Level 1 Level 1 (0 points)
    hatetea58 wrote:
    first, which version of imovie do u use. Only imovie 08 and 09 can support avchd files. Addtionally, h.264 codec also cant be accepted by imovie. dv and mpeg codec are proper.

    I use iMovie 09 8.0.6 (821) on an Intel platform.

    I don't understand your statement - "h.264 codec also cant be accepted by imovie. dv and mpeg codec are proper". The clip I imported is h.264 video codec, AAC audio codec, in an .m4v container, which I think means MPEG-4 container.
  • Alan McDonley Level 1 Level 1 (0 points)
    But now I do see a problem. The converted .m4v plays fine in VLC, but iMovie lost the audio when it imported. I guess I am going to have to transcode the audio.