Ironic: AVCHD is not a valid format to edit?

[tmw]

I see irony in statements that AVCHD is not a valid format to edit

Back in 2004, when my camcorder recorded MPEG2 (DVD format), it was a challenge to edit the files because so many editors couldn't deal with MPEG2 natively. People said it was a distribution format, not an editing format, and talked about the blessings of DV with only intraframe compression and much higher bitrates.

Now, DV has moved to HDV, which as I understand it is mpeg2 with intraframe compression. Many software programs have figured out how to deal with it.

Am I the only one who sees the irony, that the distribution format (mpeg2) has become the source format (in HDV)?

Also, now that the Canon Vixia HF series records AVCHD in 24 mbit/sec, is there any benefit to HDV at 25 mbit/sec? Would an HF that records HDV to flash be viable (clearly it can handle the bit-rates)? Or, if AVCHD is really more efficient than mpeg2 (I don't know, and I'm curious what others think), could the HF11 actually be better than HDV?

Okay, flame away at me. Tell me why the world won't move to AVCHD in 4 years time...

[redwudz]

I don't know that AVCHD is not a valid format for editing, but any highly compressed format is more difficult to edit. For example Xvid has keyframes set by default at every 300 frames. Frame accurate cutting is very difficult and usually requires re-encoding and some quality loss. A lossless format like HuffyUV or similar would be a much better choice for extensive editing. Or DV-AVI which is all keyframes, though not lossless.

If you re-encode a AVCHD through several generations, then you may not have much of any quality. Conversion to a lossless format, then back to AVCHD would be my choice for extensive editing. But you will need a lot of hard drive space.

And tmw, in the future please use a more descriptive subject title in your posts to allow others to search for similar topics. I will change yours this time. From our rules:

Try to choose a subject that describes your topic.
Please do not use topic subjects like Help me!!! or Problems.

Thanks,
Moderator redwudz

[edDV]

I see irony in statements that AVCHD is not a valid format to edit

Back in 2004, when my camcorder recorded MPEG2 (DVD format), it was a challenge to edit the files because so many editors couldn't deal with MPEG2 natively. People said it was a distribution format, not an editing format, and talked about the blessings of DV with only intraframe compression and much higher bitrates.

Now, DV has moved to HDV, which as I understand it is mpeg2 with intraframe compression. Many software programs have figured out how to deal with it.

Am I the only one who sees the irony, that the distribution format (mpeg2) has become the source format (in HDV)?

Low compression MPeg intraframe (>20Mb/s) has been a production format since around the late 90's. Sony created IMS (MPeg) format long ago with the intent for multi-generational editing in the industrial market. But that isn't the same as the 4-8 Mb/s MPeg2 used for Mini-DVD. They were tightly compressed and difficult to decode on the fly for scan/scrub with CPU's of the time which is the essence of editing. You need to find the edit point. Also, the high compression used caused severe generation loss especially when compared to DV format.

Zoom ahead 4 years and computers are 10x faster and on-the-fly MPeg2 decoding has improved so yes, you can now scan/scrub Mini-DVD with a quad core but the generation loss is just as bad.

Now we have AVCHD (MPeg4, h.264) which has the same issues with 2008 consumer level CPU's (e.g. low end Core2 Duo). Also the high 8-14 Mb/s compression used to fit SD cards causes significant generation loss compared to 25 Mb/s HDV (MPeg2) which recodes better. Prosumer versions of AVCHD operate at 25 Mb/s and Pro H.264 (AVC-Intra) uses 50 or 100 Mb/s to max editing and multi-generation quality.

So yes, computers get faster and codecs get more efficient and all this will move on in the next four years.

Also, now that the Canon Vixia HF series records AVCHD in 24 mbit/sec, is there any benefit to HDV at 25 mbit/sec? Would an HF that records HDV to flash be viable (clearly it can handle the bit-rates)? Or, if AVCHD is really more efficient than mpeg2 (I don't know, and I'm curious what others think), could the HF11 actually be better than HDV?

Currently HDV is better supported in software and matches well to the typical Core2 Duo. HDV also recodes with less loss than H.264. HDV has a big brother for broadcasters called XDCAM which uses very similar MPeg2 but has user selected bit rates from 15-35Mb/s. MPeg2 is "still" used by broadcasters because of better multi-generation performance.

The next generation h.264 based broadcast format (AVC-Intra) is frame by frame intraframe h.264 compressed only at 50 or 100 Mb/s. That gets you top quality.

[edDV]

Further, AVCHD remains difficult to edit. Consumer edit programs convert to MPeg2 on import to give the typical customer some responsiveness. This extra conversion further reduces quality.

High end edit systems offer "native" AVCHD which is sluggish except on the fastest quad core. They encourage use of a digital intermediate format (e.g. Cineform, Apple intermediate, etc.) to make AVCHD responsive. The recode losses remain.

Now if you shoot 24 Mb/s and use high end edit software and have a fast computer, you will get good results with AVCHD. Problem is most AVCHD customers have lower end computers and must buy the Platinum level consumer software to import AVCHD.

[tmw]

Thanks for your insight. I'm constantly amazed at the difference between broadcast and consumer formats, especially when they take slightly different paths. I always find myself learning from the variety of experiences and posts here, so thank you for sharing.

P.S. Sorry about the inaccurate subject line. I'll try to work on that.

[edDV]

Best way to summarize, broadcasters and videographers seek to make money from these formats while consumers want apparent convenience and lowest initial expense.