Editing HD on a slower laptop

[sascho]

Hi everyone,

Not sure if this will work in the end: I am going on a longer trip and need to save weight where I can, but still want to edit AVCHD footage. I own a Lifebook P7120 laptop which is extremely small and is able to edit SD footage (using Edius 4.6), but of course with HD I get into trouble, given that it runs on a 1.2GHz single core M753 and 1GB RAM. I could get a Vaio TZ with dual-core but that would be the most expensive option.

My question: There are various formats I can convert the AVCHD footage into with Procoder Express. Which one would be least demanding during editing? Is anyone actually editing on such a low-spec machine? Is there anything else I could try in order to make it work?

Any suggestions would be very welcome.
Sascha

[Bluetongue]

Sascha
Convert to CanopusHQ AVI, if you can edit SD footage this should make it possible in HD. The problem with slow computers is in the conversion during capture to HQ but once you have it there there are usually no problems
Regards Barry

[sascho]

Thanks a lot Barry, I tried this and it helps to make the playback a bit more fluent. It still stutters a lot though. Are there any settings I could play with?

[Bluetongue]

Sascha
No the 1.2G processor is not really up to it, what you have is about as good as it gets. Even in HQ AVI there is a lot of data to move around.
The Accepted minimum for HD is a 3Ghz processor and preferably with an 800 Mhz FSB to allow conversion on capture
Regards Barry

[STORMDAVE]

It's time to upgrade. You can get away with a good HP laptop for around $1,000.

[JTE48]

since this sort of touches on a question of mine I thought I would ask . . .

Why is it that Canopus HQ format AVI files provide more realtime performance than native MPEG-2 streams? I did a test for a 10 second clip captured as native MPEG-2 and then as Canopus HQ and both files were about 79-80MB. So if the file sizes are roughly the same what gives?

[Bluetongue]

since this sort of touches on a question of mine I thought I would ask . . .

Why is it that Canopus HQ format AVI files provide more realtime performance than native MPEG-2 streams? I did a test for a 10 second clip captured as native MPEG-2 and then as Canopus HQ and both files were about 79-80MB. So if the file sizes are roughly the same what gives?

I am surprised the file sizes were the same, to give you an idea
1 Hour of Native HDV should be around 13 Gb
1 Hour of HD CanopusHQ AVI should be between 45 and 50 Gb
for them to be the same the AVI would need to be in SD format
For your first question with the CanopusHQ file every frame is a picture in its own right
For Native HDV or MPEG the first frame is a picture and the next 14 are an encoded difference between the present frame and the previous frame and in some cases dependng on the structure the encoded difference is between the current frame, the previous frame and the one to come. Tryed to simplify the answer as much as possible.
The MPEG file requires the CPU to do a lot of calculations to reconstruct each frame where with the CanopusHQ the information can be just passed straight on to your graphics card
Hope that helps
Regards Barry

[GrassValley_BH]

Barry summed it up well...

Canopus HQ, like DV, is an intra-frame compression format, so each frame is an individual, discrete unit that can be decoded on its own.

Long-GOP MPEG-2, as in HDV, DVD-compliant MPEG, and most other MPEG-2, on the other hand, contains mostly "derived" frames. There are I-frames, usually one every 12-15 frames, but decoding a non-I-frame requires decoding its reference I-frame, and the frames between it and its reference I-frame, if any.

Another slowdown with Long-GOP formats is that it's much more difficult to "jump to" the right section.

Imagine if you have a large book, but each chapter is the same number of pages. If you know the number of pages per-chapter, you can guess approximately where a given chapter will be and open it to a page reasonably close to the chapter you're trying to get to. On the other hand, if the number of pages per chapter vary, you'll have to flip through a majority of the book's pages to get to the chapter you want.