AVCHD 720p/60 a problem?

Started Feb 18, 2009 | Discussions thread
LizaWitz Regular Member • Posts: 461
Go read the AVCHD specs

First off, you repeatedly contrast AVCHD with "MPEG2". You're in error- AVCHD is H.264 video in an MPEG2 trasnport stream. HDV is also an MPEG2 transport stream. But you seem to be confusing codecs and file formats, and my post was about file formats (the H.264 codec in AVCHD is fine).

florinandrei wrote:

Number two, this is the old, traditionalist point of view (that AVCHD
is some kind of sub-par format).

AVCHD IS, in fact, a subpar format. There is absolutely no reason to use it, unless with a random access storage device like a hard drive or flash.

I was wrong when I typed "tape", I meant to type DVD. AVCHD was created so that video could be written out to DVD recorders at a limited fixed bandwidth, and thus it interleves the audio and video data from various frames into data packets at a fixed rate--- this fixed rate is critical for Tape (and is why a transport stream is used for HDV) but its also critical for DVDs.

Its irrelevant for flash and hard drives which are perfectly capable of random access, and thus should create MP4 or MOV files. Apple solved this very problem-- for random access devices-- about 20 years ago, and the solution is an open standard and is the Quicktime file format, also known as the MPEG 4 file format.

The codec used by AVCHD is H.264 which is also part of the MPEG 4 standard and is variable bit rate. Spreading frame data all over a transport stream and interleaving it with the audio data is wasteful and causes most people to transcode their video when bringing it into an NLE.

That there are NLEs that will work with AVCHD as is, is actually quite a travesty-- cotnrary to showing my statements to be outdated, it shows the extraordinary lenghts software developers have had to go to to work with this format.

And that means things like realtime effects or realtime previews of compositions are more difficult or require a more expensive machine, or simply don't happen (or happen at a really low framerate) because the NLe is spending so much time trying to piece the video together that is strewn all over.

It used to be that MPEG2/tape combination was king.

Irrelevant. Its not like I was advocating for HDV. H.264 is a fine codec, but putting it in a transport stream like AVCHD does is pointless, and counter productive.

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.

You're confused. You seem to think the debate is between MPEG-2 codec and the H.264 codec. This is not the point at all. Yes, H.264 is better than MPEG-2. No question. Its wrapping it in a tape oriented transport stream as AVCHD does that's outdated and counter productive.

The video can simply be written out to MPEG-4 standard files, usually ending with .MP4. Some cameras do this now, such as the Xacti.

The workflow for this is really conveneint-- you just copy the files onto your hard drive. No loging and no conversion necessary.

And its far more efficient for an NLE to work with an MP4 file where it can quickly find the frame it needs... than an AVCHD mts transport stream where it has to hunt around and recreate the data it needs.

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.

AVCHD and AVC are not the same thing, and AVC is not a codec. H.264 is a codec and H.264 with certain parameters can be called "AVC", but this is not relevant to this debate, its only where AVCHD got part of its name.

There's nothing wrong with H.264, its a fine codec. Wrapping it in a MPEG-2 format transport stream is what is foolish.

Actually, its kinda ironic that this whole time you were objecting to me and in doing so defending MPEG-2 (the part of AVCHD which is not H.264 is the transport stream which is right out of the MPEG-2 standard... probably because sony already had the tech lying around from the HDV days) while seeming to think I was defending MPEG-2.

Finally, the era of edit-friendly formats for anything but the
highest-end devices is over.

Only so long as people are fooled into thinking that AVCHD is a reasonable capture format. Its kinda funny that you are arguing against me, but you don't even understand the basics of this standard. You've fallen for marketing.

There's really no reason that this "era" should be over. In the past we were bound by tape and thus very limited in capture formats.

That is not the case today. Xactis capture into MP4 files, and they did so because it was actually cheaper--- no royalty to pay for the AVCHD "Standard" which buys you nothing. Xacti's top out at $600. They are not "high end".

High end machines are more and more starting to capture in NLE friendly formats-- like the SxS and P2 formats, and JVC recently announced a $5000 camera that captures to MP4 or MOV files.

Since AVCHD provides NO ADVANTAGES over straight MP4 files, and since anyone licensing AVCHD has to license MPEG-4 anyway (to get the H.264 codec) there is no reason not to store in the edit friendly MP4 format.

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