AVCHD 720p/60 a problem?

Started Feb 18, 2009 | Discussions thread
florinandrei Regular Member • Posts: 483
some observations

LizaWitz wrote:

AVCHD is a poor format for cameras that store on SD cards and not
tapes. They really should just write out MP4 files, as there's no
reason to use AVCHD if you aren't making a tape based camcorder.

Number one, AVCHD is not used with tape camcorders. Those use MPEG2. Currently, HD camcorders either use MPEG2 and store on tape, or use AVCHD and store on SDHC (flash) or hard-drives.

Number two, this is the old, traditionalist point of view (that AVCHD is some kind of sub-par format). The fast progress of the industry is negating it.

Just look at the new AVCHD camcorders, such as the Canon HF series and the like (HF11 etc.) and compare them to MPEG2-based tape-based HD camcorders. It used to be that MPEG2/tape combination was king. Not anymore. In fact, MPEG2/tape has reached its peak, it's a mature technology that can only improve incrementally. AVCHD/flash keeps growing, and is already at the same level from the p.o.v. of image quality.

I own a Canon HF100 and it beats the cr** out of many MPEG2/tape HD camcorders. When it was released last year, it was competing for the first place in that price range against MPEG2/tape devices such as the HV30 or the other ones from Sony. I'm not sure what the situation looks like this year, but like I said, AVCHD can only move up, while MPEG2/tape has hit the ceiling already.

Also, most Blu-Ray titles nowadays use the AVC codec for the video track and it looks great. A few ones use MPEG2 (mostly old movies or cheap transfers), and finally some use VC1.

In the high-end, professional arena, things are indeed a bit different. MPEG2/tape still dominates, but probably just because it's a slow-moving, cautious market. Even there there's a two-pronged attack on MPEG2: on one hand there are signs that AVCHD is encroaching that space too, on the other there are unconventional technologies like the RED cameras using proprietary codecs that surpass everything else by a wide margin.

http://www.red.com/

In any case, MPEG2/tape's days are numbered in all markets, and AVC is emerging as the most pervasive codec for video capture and distribution. It's only a matter of time.

Anyway, when you import your footage from an AVCHD camera, generally
you'll convert it to some other format on import (one of the
downsides of AVCHD is that it can't be worked with natively) ... when
you do this you'll give up compression but you'll end up with
something easier to edit.

Not necessarily.

Many (if not all) AVCHD camcorders nowadays produce AVCHD files which are 100% compatible with the AVCHD spec, which is a subset of the Blu-Ray spec. So if you don't need to process white balance and stuff like that, you can just edit and author, and so put your material on Blu-Ray directly, with no quality loss due to multiple transcoding steps.

There's no need to transcode the whole file just to edit - in doing so you affect the whole file. You really only need to rebuild the first or last GOP. More and more applications nowadays are starting to support this kind of process (it's becoming a selling point and they brag about it on their websites).

I can't say for sure, but I'm under the impression that some digital cameras which can shoot AVCHD produce video tracks which may be compatible with the BD / AVCHD spec, therefore requiring only re-encapsulation (which is lossless), as opposed to a full decode-recode process (which is lossy). Or the whole file may be already compatible, no processing required at all. You have to try to tell for sure.

Finally, the era of edit-friendly formats for anything but the highest-end devices is over. It was gone when standard-def DV camcorders died. Nowadays we have to deal with inter-frame compression. I'm not very happy about it either, but there's nothing I can do about it. Yes, you may convert it to intra-frame for processing, but you have to judge each case on its individual merits, and figure out whether you truly need to do that or not.

It may happen that the high-end, professional tools will use edit-friendly (intra-frame compression) formats, if things such as the RED cameras become more popular. Time will tell.

An alternative would be to convert the AVCHD to MP4 files and thus
keep the compression level, and smaller files.

Well, it depends on what's the target format, doesn't it?

If it's Blu-Ray (or AVCHD, which is Blu-Ray with additional restrictions, but can be burned on DVD), then you are going to end up with some kind of AVCHD files one way or another.

If it's for Internet distribution, then sure, convert it to MP4, and probably make it 720p30 too. Or 720p15 if bandwidth is a concern.

If it's just home videos which are never going to be distributed, and for some reason you think BD / AVCHD is not for you, or you want to just keep the movies on a computer hard-drive forever, then just keep the originals. Any decent computer should be able to play them nowadays, and even more easily in the future.

By the way, MP4 is not inherently smaller than AVCHD. If video is AVC and audio is AAC, you can either encapsulate them in AVCHD (M2TS files) or MP4 and the sizes are going to be pretty much the same.

What matters most is the video track, which codec is used, the depth of the compression settings, etc.

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