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Author Topic: MPEG2 vs AVCHD  (Read 6918 times)
RFPhotography
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« on: August 17, 2012, 06:48:40 PM »
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Wondering what the comparative might be between these two formats in terms of quality. 

It's said that, for example, h.264 has the quality of MPEG2 at about half the bitrate.  So, broadcast HD quality at 20 to 25 mbps in MPEG2 is about the same as h.264 at around 12 mbps. 

Is there a comparative for AVCHD vs. MPEG2?  I'm thinking specifically in terms of the GH2.  In stock (i.e., unhacked) mode it records at about 24 mbps, I think.  I think, too, that AVCHD uses h.264 or is basically the same as h.264 so does that answer the question?

Thanks.
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Chris Sanderson
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« Reply #1 on: August 17, 2012, 07:29:55 PM »
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Encode your video with each and make your choice based on the playback medium - I believe it rather depends on the amount of motion and the required bitrate.

My encode choice is nearly always H264 [EDIT] - for the web at low bitrates.
« Last Edit: August 18, 2012, 11:27:19 AM by Chris Sanderson » Logged

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« Reply #2 on: August 17, 2012, 11:18:19 PM »
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Wondering what the comparative might be between these two formats in terms of quality. 

MPEG4 is the codec standard - AVCHD and H.264 are two different variants of MPEG4. What you need to be comparing is MPEG2 and MPEG4.

Both can be made to look equally good, if time and hard disk space were not a concern. MPEG4 was developed for a more efficient compression in terms of space - so if hard disk space is a concern this is preferred. HDCAM SR is MPEG4 based.

Quote
So, broadcast HD quality at 20 to 25 mbps in MPEG2 is about the same as h.264 at around 12 mbps. 

Broadcast quality according to big networks is a minimum of 50Mbps interframe at 8-bit 4:2:2 chroma subsampling from a 1/5" 3CCD Sensor (12.7mm) - and both MPEG2 and MPEG4 are interframe codecs. Whatever you shoot, you'll still need 50 Mbps to pass muster. 1/3" 3CCD cameras and lower are not accepted. There are always exceptions, of course.

The GH2 unhacked is not a broadcast quality camera. Until August 30th or so, the cheapest camera that records directly to a broadcast quality codec (without using an external recorder) is the Canon C300. After that date, it might be the Blackmagic Cinema Camera. I say 'might' because the BMCC has a small sensor and it will probably be tested specifically, but I don't see any reason why it should fail.

Another cheap option is the Nikon D800 with a Ninja 2.

AVCHD is not the same as H.264 - think of them as twins who look the same but are not - both daughters of MPEG4. However, for all practical purposes, they have the same 'sort' of characteristics and issues.

Your choice of codec would depend on your workflow and specific delivery requirements.
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« Reply #3 on: August 18, 2012, 12:55:54 AM »
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I think our OP is talking about what setting to record with, I think he is correct in thinking that AVCHD is the better option.

----

As for 'broadcast' I think the out stream is as he suggest around 20mbs, Id guess way lower

Why one would need an in stream of 50mbs seems baffling to me, I guess its a 'safe' that lets video camera people be off with their exposure..
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« Reply #4 on: August 18, 2012, 04:01:38 AM »
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Yes, I confirm that the gh2 has not passed
The broadcast requierements  and therefore
Not recognized for tv.

I've heard however that the hacked amazed
The techs But they won't take it into consideration
As they base themselves only on factory product.

and the hack doesn't solve the problem of 4:2:0

------------------
The Sarresh infos are correct

If it's of some help I put here the requierements of the spanish TV (TVE)

Codification.
Uncompressed accepted
Compressed MPEG-2/4  4.2.2
Aspect ratio: 16:9 / if original footage 1.85:1, 2.35:1...will be delivered in 16:9 letterbox without lost of original information. It is not allowed to transform footage to 16:9 using pillar box (lateral) except from 16 and 35mm cinema o historical tv footage in 4:3
Format: progressive is prefered/1080 50i 4:2:2 8 bits
For the INTRA no less than 100 Mbps (needs to keep quality for 4 or 5 generations)
For the formats that work in Long GOP the bitrate minimum is 50 Mbps
For the footage that will need an important post production intervention until TVE adopts a definitive format, it should be delivered in HDCAM-SR 440Mbps 10 bits
XDCAM 4:2:0 is not accepted
Less than 50 Mbps is not accepted
TVE uses MXF as a standart
Formats:
-XD CAM HD 422 50Mbps 4:2:2 8 bits MPEG-2
-AVC-I 100: MPEG-4/H.264 100Mbps 10 bits
-DVCPRO HD 100Mbps 8 bits
-DNxHD at 8 or 10 bits for mixing formats at the minimum (or above) bitrate allowed
Image sequence admited: TGA rgb-rgba / TIFF rgb-rgba / PAL D1
Camera's sensors accepted: CCD (x3 RGB), resolutions inferior to 768x576 are not allowed
Compression guide delivery:
MPEG-2  1920=80 Mb/s high level
MPEG-4 1920=80 Mb/s 4.1
Satelite transmitions: MPEG-2 42Mbps and MPEG-4 25Mbps in 4:2:2
Animated images: TGA 32 bits 72ppp and TIFF 32 bits without limit in resolution
Vectorial accepted: .AI and .CDR
Luminance levels 8 bits: 16-235 225 values
Luminance level  10bits: 64-960 897 values
The spanish national tv uses 720P
Safe area: 3,5 % of 16:9
Audio is no less than  256Kbps, 16 bits/canal. It's not allowed 192 in vav o bwf
For the images that will need cropping, the max resolution is 6400x4569 px at 300ppp and minimum is 1536 x 1152 px at 72ppp
.PSD are accepted included no merged layers
jpeg are not accepted

« Last Edit: August 18, 2012, 06:03:18 AM by fredjeang » Logged
RFPhotography
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« Reply #5 on: August 18, 2012, 06:27:23 AM »
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Thanks all.  This is the information I was looking for. 

Fred, the Spanish TV information doesn't really apply here in Canada, or North America for that matter.  A lot of what is produced here is still 720.  In Canada, at least (can't speak for the States), 'broadcast quality' is really a lack of quality.  The major cable and phone companies that offer TV service compress the crap out of their signals and send through to the end viewer something on the order of 10 to 14 mbps.  The resultant drop in picture quality is very evident if you are able to compare over-the-air HD to cable HD. 

Sareesh, I understand MPEG2 and MPEG4 are both interframe codecs.  My point was that if MPEG4 is more efficient and the standards are based on MPEG2 then perhaps MPEG4 would be useable at a lower bitrate.  Maybe not, I'm not sure.  But when you see news reporters carrying around and broadcasting from small camcorders it makes you wonder.  As you say there are exceptions.

Have to wonder about the standards as well when you know that major production studios are using DSLRs to shoot all or parts of some television shows. 

I think the biggest issue might be the 4:2:2.  I think there is a hack out there though that will do 4:2:2. 

The D800 isn't capable of 1080/60. 
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fredjeang
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« Reply #6 on: August 18, 2012, 06:32:26 AM »
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Bob, the same here. Those are the requierements they impose, but the signal that reaches us is also 10 to 15 ish mbps...

A Hack that allows 4:2:2 ? where is the link? I want the link.
« Last Edit: August 18, 2012, 06:36:17 AM by fredjeang » Logged
Sareesh Sudhakaran
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« Reply #7 on: August 18, 2012, 06:59:00 AM »
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I was under the impression ESPN broadcasts at 720p59.94, but have they upgraded to true 1080p59.94? Is there any channel in North America with a 1080p60 pipeline?

Also, the 50 Mbps bit rate is probably based on a single link HD-SDI SMPTE 292M standard, which at best is 1080p29.97 (or 1080i59.94) or 720p59.94. So if somebody wants to shoot 1080p59.94 the interframe data rate would be 100 Mbps.

Does the Panasonic GH2 hack allow 60fps progressive? Wow, that's brilliant. Even the C300 doesn't give that. The FS100 does, but I don't know if any external recorder can make that happen over the HDMI link it provides.
« Last Edit: August 18, 2012, 07:19:07 AM by Sareesh Sudhakaran » Logged

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RFPhotography
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« Reply #8 on: August 18, 2012, 07:57:02 AM »
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Fred, I could be wrong on the 4:2:2.  I've been trying to read a lot of the stuff that's out there on the GH2 and may not have that right.  If I can find anything again, I'll post it.

Sareesh, natively the GH2 is 60i but one of the hacks that was out there was testing progressive. 
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Sareesh Sudhakaran
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« Reply #9 on: August 18, 2012, 08:19:52 AM »
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Bob, the simple answer to your question is: Yes, MPEG4 is theoretically a more efficient codec than MPEG2. The H.264 variant is even better.

If the two were suitcases, an MPEG4 suitcase can stuff in more ironed shirts than an MPEG2 suitcase - but at the end of the trip how many of your shirts will still stay ironed? My personal tests have convinced me there isn't an  'absolute difference' between the two. MPEG4 is a brilliant codec standard, but it makes a lot of compromises to achieve that level of compression. It's like eating sugar-free candy - a purely subjective thing all said and done.

I highly recommend testing short bits of video for your workflow and judge for yourself what works. The deck is already stacked in favor of H.264, so your options are limited as far as delivery is concerned.
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« Reply #10 on: August 18, 2012, 11:07:25 AM »
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Sareesh,

Broadcast in the US is either 720p59.97 or 1080i59.97.

I have shot 720p23.98, delivered as 1080p 59.97 HDcamSR and no country has rejected it for Quality Control.  Of course they couldn't tell what the original was shot with, and I couldn't either if I hadn't shot it myself:)
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Bruce Alan Greene
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« Reply #11 on: August 18, 2012, 11:37:57 AM »
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I have shot 720p23.98, delivered as 1080p 59.97 HDcamSR and no country has rejected it for Quality Control.  Of course they couldn't tell what the original was shot with, and I couldn't either if I hadn't shot it myself:)

Care to name which networks? Smiley
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RFPhotography
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« Reply #12 on: August 18, 2012, 11:49:19 AM »
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Difficult for me to do testing, Sareesh.  I don't own the GH2 (or any other flash capture video camera).  All I have are old HDV tape-based machines that wouldn't be relevant for this kind of testing.

I wonder if Bruce hasn't hit on the real crux of the issue.  If you can deliver the end product that's required and it's indistinguishable that it was shot as something else, does it matter?
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« Reply #13 on: August 18, 2012, 03:45:17 PM »
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MPEG4 is the codec standard - AVCHD and H.264 are two different variants of MPEG4.
This is not correct. H.264 and MPEG 4 AVC / Part 10 was developed jointly by the ITU and the MPEG guys. If anything, the codec in question was started by the ITU guys in 1998, the MPEG people only joined forces in 2001.

AVCHD seems to be just a file-container/set of constrictions that happens to use H.264/MPEG4 AVC.

http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC

http://en.wikipedia.org/wiki/AVCHD
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RFPhotography
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« Reply #14 on: August 18, 2012, 05:46:14 PM »
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How many angels can dance on the head of a pin?   Grin

I think that's splitting hairs.  A distinction without a difference.  Irrespective of that distinction, the information I got was what was needed and asked for.  So in the end it's all good.
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« Reply #15 on: August 20, 2012, 10:20:25 AM »
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sorry, don't know the exact networks.  Only the distributor knows this, and they're not giving full reports....It was QC'd here in the US, and passed in every format.
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