Confusion on codec

[Tim Dashwood]

Originally Posted by Robert Rogoz

What I was confused about is the use of term "ProHD", which is totally different from let's say HD100.

"ProHD" is just a moniker for JVC's line of affordable professional HD cameras, decks, encoders, and accessories. It isn't a format it's just a "family" of products.

Originally Posted by Steve Mullen

1) It would make no sense to encode video as long-GOP MPEG2 using the JVC encoder and then "write them into the XDCAM EX codec." First, nothing "writes" into a codec. Second, already encoded data would never be sent into a codec. To use previously JVC encoded data, the data would have to be decoded to baseband and then re-encoded as XDCAM EX-- causing a loss in quality.

2) Streams are not sent into a codec as .mov or .mp4. Encoded data coming-OUT of a codec IS THEN wrapped as .mov or .mp4.

The flow you describe is backwards.

I'm just trying to explain this in a way that the layman will understand.
I think most forum members are familiar with the distinction between a wrapper (Quicktime, Windows Media, Flash, AVI, etc.) and a codec (HDV, XDCAM EX, XDCAM HD, ProRes 422, Photo-Jpeg, DV, Cineform, etc.) but may not realize that XDCAM EX is still compressed mpeg-2 long-GOP 4:2:0 exactly like "HDV" with the only real difference being a 35mbps VBR option and uncompressed audio. Maybe I should have used the term "compress" instead of "encode."
Does this statement make more sense?
The HM series cameras use JVC's mpeg2 compressor to compress mpeg2 long-GOP streams at 19/25/35 Mbps and then encode them into the XDCAM EX codec wrapped as either .mov or .mp4.

Originally Posted by Steve Mullen

When .mp4 is written to SDHC by the HM100 -- are these files seen as XDCAM EX? You say YES, but at no point in the HM100 brochure are there the words XDCAM EX. Only the word ".mp4." And, there are the JVC ProHD Clip Manager and a FCP ProHD Log and Transfer Plug-in just for the .mp4 files. If these files seen as XDCAM EX, why would FCP need a ProHD Log and Transfer Plug-in?

Please read any information with regard to recording formats in the official brochure with an understanding that JVC have publicly licensed XDCAM EX from Sony and are using it in both products but that doesn't necessarily mean they also negotiated the right to use the logo or even claim to use "XDCAM EX" in their marketing materials. If the multiple threads on dvinfo.net are any indication this could prove to be detrimental to the potential sales and public understanding of the HM line of cameras.

Originally Posted by Steve Mullen

1) The box could, as some have suggested, be a big dongle that helps pay for the right to write XDCAM EX compatible .mp4. (The camera would do the actual wrapping.)

2) Or, it could have a Sony encoder -- in which case why isn't JVC promoting the fact you get Sony encoded XDCAM EX when you buy the box? Perhaps, this is part of the license?

3) Or, it could contain "something" -- perhaps OEMed from Sony that wraps the JVC encoded data to .mp4 files that are compatible with XDCAM EX. (Tim, perhaps this is what you were trying to describe.) However, I thought wrapping is always done by the encoder itself.

Ultimately yes the KA-MR100 SxS box is a dongle for unlocking mp4 wrapping to either SxS or SDHC so it is irrelevant whether the OEM hardware/software exists in the camera or in the KA-MR100.
Either way it definitely isn't a Sony mpeg2 encoder.
An additional clue might be that to use the KA-MR100 with the HD200B or HD250 an additional box called a KA-UM100G mounting adapter is required to interface the firewire m2t compressed stream with the KA-MR100. Is the KA-UM100G encoding the m2t stream as XDCAM EX and wrapping it as mp4?

Originally Posted by Steve Mullen

1) Without the SxS box -- can the HM700 write the same kind of .mp4 files to SDHC as can the HM100? If so, do you get the JVC JVC ProHD Clip Manager and a ProHD Log and Transfer Plug-in?

No. As mentioned above the KA-MR100 SxS is required to unlock mp4 wrapping but once it is attached you can also record those files to SDHC. I've haven't seen the JVC software yet but I can tell you from personal experience it is completely unnecessary for mp4 if you've already installed the Sony XDCAM EX transfer software. Quicktime wrapped files only require the XDCAM EX quicktime component which is installed with FCP6 or the Perian open-source version can be downloaded for free. Windows users can install the XD Decode XDCAM component for Quicktime but unfortunately it isn't free.

Originally Posted by Steve Mullen

2) Why does the HM700 brochure always say .mp4 (the kind compatible with XDCAM EX) is written to SxS and SDHC simultaneously? Does that mean you always need both types of cards inserted?

No. When I tested the HM700 with KA-MR100 I only had a SDHC card and I successfully recorded both .mov and .mp4 files to it.
As mentioned above the wording in the brochure is likely JVC's way of mentioning XDCAM EX without infringing on the legal restrictions of their OEM agreement with Sony.

[Jack Walker]

Thank you, Tim. Things are much clearer now.

With a little bit of searching, there is additional information available:

It seems that the HM700 is JVCs in-camera implementation of its new SxS recorder for the HD200 and up cameras. Here is the initial press release from JVC that explicitly talks about the XDCAM EX format:
JVC Press Release - IBC 2008

Some of the original confusion may have been due to the fact that the XDCAM EX format supported 25 Mbit/s CBR (SP mode) and 35Mbit/s VBR (HQ Mode), but not 19 Mbit/s (the JVC ProHd modes), but JVCx HM cameras do support 19 Mbit/s. However, it appears that with the agreement between JVC and Sony, 19 Mbit/s has been implemented within the XDCAM EX format (by JVC or Sony?). This is documented, with additional information regarding XDCAM EX for JVC in this article:
http://www.dvwonline.com/index2.php?...o_pdf=1&id=740

So it seems that JVC uses the XDCAM EX format/codec, and the format includes new features implemented especially for JVCs KA-MR100G and now the HM cameras. In the original recorder (KA-MR100G) the specs do not show 35 Mbit/s, on 19 and 25. In the new HM cameras there is 19, 25 and 35 Mbit/s,

But the only connection with Sony is the XDCAM format/codec.

And XDCAM EX refers to Sony's SxS cameras, not just the format. (Or maybe only the cameras, with the format getting that desination from the camera, making the XDCAM EX designation incorrect for the JVC cameras.)

So, there are two lines of cameras:

SONY
Cinealta line, of which the XDCAM EX cameras are at the bottom end

JVC
ProHD line, of which the GY-HM700 is the top of line, and the GY-HM100 is the handheld companion. The KA-MR100G brings the HD200+ cameras into the solid state arena and the option to record at 35 Mbit/s, while retaining the ability to record the original JVC formats to tape.

Now, as pure speculation, it would seem that the JVC/Sony licensing agreement for the XDCAM EX format depends on camera chip size. The Sony XDCAM EX is 1/2" chip, probably the minium high end producers for TV will use (such as in reality programming, where the EX cameras are popular).

The HM700, top-of-the-line JVC camera (and small profile shoulder mount) is 1/3" CCD, ruling out the camera for the Cinealta market. Meanwhile, the XDCAM EX codec gives the JVC camera the 35 Mbit/s quality that was missing from the HD200+, making the 200 a disappointment. And because of the 1/3" chips, and the high quality picture, the $500 SxS add-on is required to record the 35 Mbit/s format on this camera.

And then the JVC HM100, with its 1/4" chips. This camera is not going to compete with the quality of the 1/3" camera in most people's minds, so its given the ability to record 35 Mbit/s straight to the SDHC card out of the box, without the $500 "extra licensing fee."

So Sony's Cinealta has the high to middle range where JVCs ProHD picks up in middle to the low range -- but all in the pure professional XDCAM EX format/codec, and with uncompressed audio.

JVC includes the mov wrapper to cleanup with the Final Cut crowd, as well, probably a large part of the event market.

With the XDCAM EX format in the JVC cameras, JVC gets the 35 Mbit/s quality it sorely needs, and Sony gains ground in the format wars by getting wider use of its codec.

[Steve Mullen]

Originally Posted by Tim Dashwood

Does this statement make more sense?
The HM series cameras use JVC's mpeg2 compressor to compress mpeg2 long-GOP streams at 19/25/35 Mbps and then encode them into the XDCAM EX codec wrapped as either .mov or .mp4.

No -- there is no COMPRESS followed by an ENCODE. And, more importantly, MPEG2 data can't be "encode[ed] ... into the XDCAM EX codec" because a codec is a software/hardware component -- not a short-hand way of saying "format" even for a layman.

With MPEG2, or MPEG4, there is an encoder (the codec) that encodes digital video to a bit-stream. This bit stream is then wrapped as .mp4, etc. The wrapping can be done by the encoder chip or by a different chip.

So, how about this:

The HM series cameras use JVC's encoder to generate mpeg2 long-GOP bit-streams at 19/25/35 Mbps which are wrapped as .mov or .mp4 files compatible with the Sony XDCAM EX specification.

However, saying this implies things never stated in either brochure:

1) the HM100 and HM700 .MOV files on SDHC will be seen (reported as being) XDCAM EX files even though this is never stated to be the case by JVC.

2) the HM100 .MP4 files on SDHC will be seen (reported as being) XDCAM EX files even though this is never stated to be the case by JVC. Therefore, there is no need for the FCP plug-in that JVC developed.

3) And, most interesting of all, EITHER -- without the SxS box the HM700, unlike the HM100, can only record .MOV files to SDHC, or it can record the "same" .MP4 files as the HM100, which you say actually are XDCAM EX compatible, but JVC can't say this.

It seems like you are saying the brochures don't say explicitly what you claim to be the case -- for certain Sony/JVC reasons. I can understand this. But, I'd be happier if JVC would state the shipping camcorders would behave exactly as you report.

For example, it seems very odd the FCP plug-in is mentioned in such detail in the HM100 brochure when you say it doesn't need to even exist. I have to wonder about skipping over this tiny detail.

Reading the HM100 brochure, it certainly sounds like it writes MPEG2 in a .mp4 wrapper that it not compatible with XDCAM EX -- hence the need for the plug-in. And, if this is true, it would make sense that without the KA-MR100 box the HM700 would also write these files. Did you test the HM700 without the SxS box? Have you actually tested the HM100 .mp4 files?

To me it seems reasonable that JVC can only write an XDCAM EX compatible .mp4 files when the KA-MR100 is attached. Without the KA-MR100, the files can be wrapped as .mp4 but not using the XDCAM EX specification. Hence the need for the plug-in.

In other words, Sony is fine with .mov files being reported as XDCAM EX because its products don't write .mov files. However, its products do write .mp4 files so a license is needed.

The HM series cameras use JVC's encoder to generate mpeg2 long-GOP bit-streams at 19/25/35 Mbps which are wrapped as .mov or .mp4 files with the .mp4 files being compatible with the Sony XDCAM EX specification when the KA-MR100 is attached.

PS: The KA-UM100G is interesting. The .mt2 steam is already encoded and wrapped, so it must unwrap the data stream so the KA-MR100 can re-wrap it as .mp4. Which certainly suggests there is "something" in the KA-MR100 and it's not a simple dongle.

[Tim Dashwood]

Originally Posted by Steve Mullen

1) the HM100 and HM700 .MOV files on SDHC will be seen (reported as being) XDCAM EX files even though this is never stated to be the case by JVC.

Yes. http://www.dvinfo.net/articles/jvcpr...ges/bin480.png

Originally Posted by Steve Mullen

2) the HM100 .MP4 files on SDHC will be seen (reported as being) XDCAM EX files even though this is never stated to be the case by JVC. Therefore, there is no need for the FCP plug-in that JVC developed.

Yes it will be redundant if the Sony version is already installed. http://www.dvinfo.net/articles/jvcpr...ransfer500.png

Originally Posted by Steve Mullen

3) And, most interesting of all, EITHER -- without the SxS box the HM700, unlike the HM100, can only record .MOV files to SDHC, or it can record the "same" .MP4 files as the HM100, which you say actually are XDCAM EX compatible, but JVC can't say this.

The HM100 can record both types out-of-the-box, but the HM700 will only record .mov out-of-the-box without the addition of the KA-MR100 SxS box to unlock .mp4.

Originally Posted by Steve Mullen

It seems like you are saying the brochures don't say explicitly what you claim to be the case -- for certain Sony/JVC reasons. I can understand this. But, I'd be happier if JVC would state the shipping camcorders would behave exactly as you report.

We all would.

[Steve Mullen]

Originally Posted by Tim Dashwood

We all would.

So the topic "Codec Confusion" comes from am intentional lack of clarity in the fancy brochures. But, standing back -- it does have a certain logic to it all:

1) Given JVC's total lack of reference to XDCAM EX in relation to the HM100, it was necessary to create applications and import techniques that were fully independent of anything related to XDCAM EX. If the customer discovers XDCAM EX related stuff works -- so be it.

2) Given that the HM700 with the SxS box writes exactly the same .mp4 as does the HM100 without any box, JVC was faced with issue of what .mp4 would the HM700 write without an SxS box. Answer -- the same as with. Solution, prevent the HM700 from writing .mp4 unless the box is attached. So while the HM700 "could" write .mp4 just like the HM100 -- it won't. (And, it's the JVC encoder that writes the .mp4 wrapper for both cameras. But, it isn't allowed to on the HM700 unless you add SxS box to your camera.)

3) Although we know the JVC encoder does the encoding and the files are always compatible with XDCAM EX files -- even if JVC will not say they are unless you buy the SxS box -- we don't know if the "JVC" encoding is better, the same, or worse then is "Sony" encoding. Which means we are safer if we never say these cameras encode XDCAM EX. Instead, they write files that are XDCAM EX compliant.

4) So when JVC footnotes that certain flavors are only available with .mov files -- these files will be reported as XDCAM EX by FCP even though they are not available with .mp4 files because these flavors are not supported by Sony XDCAM EX products.

NAB should be a lot of fun for JVC because these brochures will be carried back to all parts of the world and from them, folks will develop their own interpretations of what the workflows can be. There will be Bible Study groups to parse every word. Which won't work because the important stuff is not written down. (And, I can imagine what the working press will do if JVC doesn't spell-out every detail.)

I'll bet there were lawyers involved. :)

[Steve Harryman]

Steve, nice article in Broadcast Engineering.

Thanks to both yourself and Tim for trying to make sense of this PITA issue.

[Bill Mecca]

quick question. I've been looking at the HM100 and 700. So if one shoots with the 700, without the SxS and its .mov on the SDHC cards. Can those be used in Avid MC 3.5,(PC) and what steps would need be taken. (not sure if the powers that be will go for the extra$$)

Thanks