iMovie imports .m4v without convert to AIC - This is good, right?

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.

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!

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.