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Canon XA and VIXIA Series AVCHD Camcorders
For the Canon XA25, XA20, XA10 and all VIXIA / LEGRIA Series AVCHD camcorders.


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Old February 18th, 2015, 06:25 AM   #1
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XA-25: 4.2.2 on SDI and HDMI ?

Hi

I could not find a definitive answer on this...
I understand the HD-SDI out of the XA-25 is 4.2.2 (presumably 8 bit, not 10)
Is the HDMI out identical, or is it stripped-down to 4.2.0 ?
I would like to capture uncompressed, but my capture device (Matrox MXO2 mini) has only HDMI in, not HD-SDI.

OTOH, I have a cheap SDI-to-HDMI converter (without doc): it is reasonable to believe that this device does simple "passthrough" of the SDI signal, and hence deliver 4.2.2 HDMI ?
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Old February 18th, 2015, 09:11 AM   #2
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Re: XA-25: 4.2.2 on SDI and HDMI ?

The HDMI output of any video device is typically "uncompressed" and uses 4:2:2 8-bit color is my understanding. This seems to be the standard regardless of gear manufacturer. So if you are shooting live and taking the HDMI output from the live camera, the HDMI output has NEVER been compressed.

If you record to the internal memory card of camera, most cameras do use the AVCHD compression and also drop color to 4:2:0. If you later play this video out the HDMI, the compressed video gets uncompressed for playback and does again output as 4:2:2, however the quality that was lost during original compression for recording does not come back, that is forever lost.

To clarify, an HDV camera does not output over HDMI using "HDV" compression - the video is uncompressed before playback. Same with AVCHD, the AVCHD compression is not transmitted over HDMI. Video is uncompressed for playback.

TV sets with HDMI inputs do not accept compressed signals, they are just looking for an "uncompressed 4:2:2" video source coming in. The camera (or DVD or Blu-ray player) uncompresses the video before sending out the HDMI.

EDIT: re-reading your post, I realized you wish to capture direct to uncompressed using the MXO2 Mini hardware, which I also use. Please note that capturing uncompressed HD video requires very fast RAID hard drive arrays and creates huge files. You might consider using the Matrox AVI codec instead, which does retain 4:2:2 color and is not highly compressed. User can adjust bitrate between 100-300Mbps.

Hope this makes sense

Thanks
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Old February 18th, 2015, 12:25 PM   #3
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Re: XA-25: 4.2.2 on SDI and HDMI ?

The plan is to capture in DNxHD185x, the 4:2:2 10-bit codec of my Avid editing program.
Your answer is interesting as in most (if not all) answers I saw about Canon XA camcorder HDMI ouput, there is a clear mention of 4:2:0, certainly for the XA-10 (which I also have).
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Old February 18th, 2015, 12:48 PM   #4
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Re: XA-25: 4.2.2 on SDI and HDMI ?

I follow several forums all day every day and whenever the subject of HDMI camera output comes up, everyone always says the output is 4:2:2 and that is what I'm going by, and that makes sense to me since 4:2:0 would suggest some type of compression, but the video being output is uncompressed, so even if playing 4:2:0 video from the SD card, it should be reconstituted as 4:2:2 for output (not gaining any quality though).

I use the MXO2 Mini with the PC and Premiere and the only recording options are Matrox Uncompressed or Matrox AVI (MPEG-2 I-Frame 422). Not sure if the Avid drivers let you capture directly to Avid codec or not.

EDIT: I just did a web search for "Canon XA-25 HDMI 4:2:2" and came up with plenty of info. Problem is, there are conflicting reports. One long thread laments that the HD-SDI output is "crippled" at 4:2:0, yet when I look at the Canon factory brochure, it clearly states that the output is 4:2:2 (but does not mention the HDMI color specs). Several reviewers claim that the HDMI is 4:2:2. Further, I looked at the official HDMI spec on Wikipedia and 4:2:0 was not implemented until HDMI 3.0, all previous versions used 4:2:2 or 4:4:4 from what I read. So confusing, what is the reality?

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Old February 18th, 2015, 09:15 PM   #5
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Re: XA-25: 4.2.2 on SDI and HDMI ?

Maybe think of it in the old DV audio terms.
I could record audio as 12-bit 32 kHz sample rate.
I could open that file in my DAW and save it as a 16-bit 48 kHz file.
But the new file is still stuck with the bandwidth and resolution of the original recording.
(Although the increased bit depth and sample rate may add some advantages for subsequent audio processing and effects.)
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Old February 21st, 2015, 02:40 PM   #6
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Re: XA-25: 4.2.2 on SDI and HDMI ?

If a camera is putting out true 4:2:2 through the SDI output, it is probably doing the same through HDMI since that is the HDMI spec anyway for the version on the camera (the most recent version of HDMI includes 4:2:0, but that isn't what is on the XA-2-/25/G-30 cameras). I doubt that they would have two separate data streams going on in the camera just for the hell of it.
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Old July 27th, 2015, 02:02 AM   #7
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Re: XA-25: 4.2.2 on SDI and HDMI ?

But is either of them 10-bit? Just because it is 4:2:2 doesn't require it be 10-bit, correct?
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Old July 27th, 2015, 03:40 AM   #8
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Re: XA-25: 4.2.2 on SDI and HDMI ?

Quote:
Originally Posted by Jeff Pulera View Post
I follow several forums all day every day and whenever the subject of HDMI camera output comes up, everyone always says the output is 4:2:2 and that is what I'm going by, and that makes sense to me since 4:2:0 would suggest some type of compression, but the video being output is uncompressed, so even if playing 4:2:0 video from the SD card, it should be reconstituted as 4:2:2 for output (not gaining any quality though).

I use the MXO2 Mini with the PC and Premiere and the only recording options are Matrox Uncompressed or Matrox AVI (MPEG-2 I-Frame 422). Not sure if the Avid drivers let you capture directly to Avid codec or not.

EDIT: I just did a web search for "Canon XA-25 HDMI 4:2:2" and came up with plenty of info. Problem is, there are conflicting reports. One long thread laments that the HD-SDI output is "crippled" at 4:2:0, yet when I look at the Canon factory brochure, it clearly states that the output is 4:2:2 (but does not mention the HDMI color specs). Several reviewers claim that the HDMI is 4:2:2. Further, I looked at the official HDMI spec on Wikipedia and 4:2:0 was not implemented until HDMI 3.0, all previous versions used 4:2:2 or 4:4:4 from what I read. So confusing, what is the reality?

Thanks
I think that you can't always rely on general HDMI specs to tell you what is going out of a camera port. You can find what a certain version of HDMI is capable of by looking it up on Wikipedia but the max. video quality it's capable of and how a camera manufacturer decides to use it can be two different things. Some camera manuals publish the specs for the HDMI port, some don't. I have a HD video camera that has HDMI and SDI and neither of them output uncompressed. And I thought HD-SDI was always uncompressed. Not so. For example, some cameras will output HD over HDMI when in playback mode, but drop to SD during recording mode. If the camera manual doesn't give detailed output specs for the port, then I come to no longer assume it's the highest quality, as it would seem a good selling point to include in the advertisement if it were 4:2:2 uncompressed. If that verbage is missing, don't count on it.
Marketing smoke and mirrors makes this spec confusing.

Tim,
The XF300 & XF305 are 4:2:2 50Mbps 8-bit, as I believe the C300 is. Not 10-bit.


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Old July 27th, 2015, 05:53 AM   #9
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Re: XA-25: 4.2.2 on SDI and HDMI ?

4:2:2 does NOT require 10-bit.
It defines how the color information is sampled relative to the B&W.

In terms of today's video for home user consumption the main advantage of 4:2:2 and 10-bit over 4:2:0 and 8-bit come into play when applying video effects and other DSP. That may change as versions of ultra high definition moves to the mainstream.

While in recent times digital video has mostly been 8-bit, some older DSP systems used 6-bit for chroma because it was "good enough" given the insensitivity of the eye to colors, noise in transmission and distribution channels, display performance, etc.
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Old July 27th, 2015, 06:20 AM   #10
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Re: XA-25: 4.2.2 on SDI and HDMI ?

Quote:
Originally Posted by Don Palomaki View Post
4:2:2 does NOT require 10-bit.
It defines how the color information is sampled relative to the B&W.

In terms of today's video for home user consumption the main advantage of 4:2:2 and 10-bit over 4:2:0 and 8-bit come into play when applying video effects and other DSP. T....
Exactly what I thought (and said) ... so do you now if the Canon XA25 outputs 10-bit? I am well aware of the advantages of both the color-space and the sampling rate.

I have been wanting to use 10-bit footage (of my own) for a long time as I do visual effects, 3D CGI, etc. Edius has been able to handle 10-bit footage forever, but I've never had my own stuff, just clients' footage, to experiment with in the past.

Same goes for the 4:2:2 color-space ... I occasionally have the need to shoot greenscreen, and having 4:2:2 instead of the limited 4:2:0 of the Canon's AVCHD/MP4 codec would be great. Although I am pretty sure now that the SDI out (and probably the HDMI out) supports 4:2:2.

The reason I am asking is, if I go to the trouble to get a Atomos Ninja/Samurai or the like, I want to know it is worth it.
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Old July 27th, 2015, 06:28 AM   #11
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Re: XA-25: 4.2.2 on SDI and HDMI ?

Quote:
Originally Posted by Mark Watson View Post
I think that you can't always rely on general HDMI specs to tell you what is going out of a camera port. ... but the max. video quality it's capable of and how a camera manufacturer decides to use it can be two different things.
Ain't that the truth ... so I'm learning.

Quote:
If the camera manual doesn't give detailed output specs for the port, then I come to no longer assume it's the highest quality, as it would seem a good selling point to include in the advertisement if it were 4:2:2 uncompressed.
I would tend to agree. However, unless they are flat out lying, Canon's site now says under it's detailed features listings that it is indeed 4:2:2 : "HD/SD-SDI output provides an uncompressed signal at 1920x1080 resolution with 4:2:2 color sampling and embedded audio and time code."

Quote:
Tim,
The XF300 & XF305 are 4:2:2 50Mbps 8-bit, as I believe the C300 is. Not 10-bit.
That does not bode well than for the XA25. However, it *IS* newer than the XF300/305 buy at least 3+ years. so there is some hope. But the XF series are supposed to be a class above, so I'm not real hopeful. Especially since you can't seem to get an answer on this anywhere.

I'll post here if I ever find out.

Thanks!
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Old July 27th, 2015, 08:17 AM   #12
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Re: XA-25: 4.2.2 on SDI and HDMI ?

Links saying the XA25 has 4:2:2 uncompressed output.

Canon U.S.A. : Support & Drivers : XA25

Canon XA25 Professional HD Camcorder Reviews | 2013 Pro Series | Flash Memory | HD/SD-SDI Uncompressed Port | SmartReview.com


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Old July 27th, 2015, 10:46 AM   #13
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Re: XA-25: 4.2.2 on SDI and HDMI ?

Quote:
Originally Posted by Mark Watson View Post
Links saying the XA25 has 4:2:2 uncompressed output. ...
Yah, that's what I said above in my reply to you ("I would tend to agree. However, unless they are flat out lying, Canon's site now says under it's detailed features listings that it is indeed 4:2:2 ... [snip] ").

So I am fairly well convinced that it has 4:2:2 out the SDI, but the two questions remain:

-> What about HDMI? (Would prefer HDMI as it would not send it out in a 60i signal AND can get a Ninja instead of a Samurai from Atmos.)

-> Is it 10-bit?
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Old August 5th, 2015, 08:56 AM   #14
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Re: XA-25: 4.2.2 on SDI and HDMI ?

Since my original post, I have found that the HF-G10 (consumer version of the XA-10, ancestor of the XA-20) outputs 4:2:2 on its HDMI terminal.
We can therefore certainly trust the XA-20/25 also outputs 4:2:2 on the HDMI terminal (and hence, SDI also certainly)
I haven't been able to verify about 10 or 8 bit, but I assume the latter is true.
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Old August 5th, 2015, 04:28 PM   #15
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Re: XA-25: 4.2.2 on SDI and HDMI ?

Right, but unfortunately I believe that is because HDMI is (or was) only capable of 4:2:2 at the time. So while it may be passing a signal with 4:2:2, that does not mean it was receiving 4:2:2 from the camera, and in fact was 4:2:0. At least that's what I read just recently, and also to Mark's point. Same goes for 10-bit ... you can have something be in 10-bit stream, but the source is 8-bit. Doesn't make the 8-bit any better.

However, for the XA25 at least, Canon is saying it is 4:2:2 out of the SDI ... so I would think it would be true 4:2:2 out the HDMI as well.

Still a mystery on the 8-bit or 10-bit, but if I had to bet, I would go with 8-bit.
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