Quality: HDMI Playback on HDTV vs. Firewire Capture

[jimbills]

Hi. A thousand apologies if this has been answered a million times - please point me to a helpful thread if so. I've scoured Google and this forum for hours, but I haven't found a clear answer. This is my first post on this forum.

When I preview footage recorded on HDV tape by my HV40 using an HDMI cable to my HDTV (not a live recording), the image quality looks fantastic - and what I'd expect from an HD camcorder. When I capture that footage using Final Cut Express, a Firewire cable, and the HDV 60i Apple Intermediate Codec - there is a clear loss in image quality (mostly sharpness, but also noise and color). This is before I export the video - the quality loss is seen in Final Cut itself.

This confuses me, as I've read the Firewire is supposed to deliver exactly what is recorded on the tape. I've also read that while there is a loss in quality of recording live via HDMI vs. recording on HDV tape, once it's on tape - why is there an image quality loss between viewing an HDV tape directly onto an HDTV by HDMI vs. capturing from a HDV tape via Firewire?

Is the Apple Intermediate Codec causing the loss in image quality? What is? Is there a better method to eliminate or reduce the loss in quality?

Thanks.

[blondandfun]

You expect the image to be the exact same between computer and a TV?

Wow, are you that naive? Which is worth more, your tv or your computer monitor? Think about that, and that's your answer.

If they are worth the same (which is possible), then I believe that TV's have internal chips that adjust HDMI signals to make them brighter/more contrasty. Firewires and computer monitors don't have the same expensive chips that TV's do that make everything look great.


Also, DUH, computer monitors don't have the same output as TV's. HDTV's are meant to be watchable 20+ feet away.

[jimbills]

You expect the image to be the exact same between computer and a TV?

Wow, are you that naive? Which is worth more, your tv or your computer monitor? Think about that, and that's your answer.

If they are worth the same (which is possible), then I believe that TV's have internal chips that adjust HDMI signals to make them brighter/more contrasty. Firewires and computer monitors don't have the same expensive chips that TV's do that make everything look great.

Hi. My HDTV is connected to BOTH my Mac and my HV40. The HDTV is my Mac's monitor. If the HDTV is adjusting the picture - shouldn't it be doing so for both the Mac and the HV40?

Also, I'm not talking contrast and brightness - as I'm a professional photographer, I know the difference between contrast and brightness vs. image sharpness, color, and noise.

Still, there is a definite difference in video quality between viewing the tape directly from the HV40 and from viewing it after it has been captured in Final Cut. Can someone help explain why? Thanks.

[jimbills]

Also, DUH, computer monitors don't have the same output as TV's. HDTV's are meant to be watchable 20+ feet away.

A modicum of respect would be appreciated. Thanks.

I happen to use my HDTV as my Mac's monitor. It's a long story, but basically, I have it connected mainly to preview portraits to my photo clients. Frankly, a plasma HDTV looks better when viewed from a sofa 8 feet away than any computer monitor or LCD projector.

(Also, no, I don't edit my photos using this system.)

[blondandfun]

Wrong again. When you hook up your camcorder directly to TV that's a completely different technology than hooking up your computer to your TV. The 2 are NOTHING alike, because the signals are different in both cases. All TV's have internal chips which adjust images to their liking

The signals from the HV series interact with the TV from HDMI differently than do your mac. It's the same tired question of "why video look brighter on camer's LCD than on computer?" silly foolishness. STOP YOUR ONE-DIMENSIONAL thinking. NOT ALL MONITORS/TV's LOOK THE FREAKING SAME UNDER ALL CIRCUMSTANCES!!!!

You can't compare apples to oranges. If you want to achieve the same quality, then I suggest you compare to blu-ray from a blu-ray player directly connected to a HDTV, to your initial camera_HDTV connection. Then you can compare.

[jimbills]

Wrong again. When you hook up your camcorder directly to TV that's a completely different technology than hooking up your computer to your TV. The 2 are NOTHING alike. All TV's have internal chips which adjust images to their liking.

You can't compare apples to oranges. If you want to achieve the same quality, then I suggest you compare to blu-ray from a blu-ray player directly connected to a HDTV. Then you can compare.

Why would image sharpness and noise be affected by the TV? Isn't noise created from acquisition and compression schemes rather than a TV's interpretatation? Is image sharpness as well?

Are you basically telling me that there is no loss in image quality in the captured video in Final Cut compared to the raw data from my HDV tape using my current capture method? That basically, I'm seeing an image quality loss solely from my Mac to my HDTV as opposed the HV40 to my HDTV?

If this is your message - that the image quality loss is purely perceptual and that a Mac is unable to display the image quality on an HDTV that an HV40 can, and tha my current capture method is as good as it can be - then please let me know. Thanks.

[Janke]

B&F, why so hostile?

Jimbills: Are you watching the footage in full HD res on your computer, i.e. does it have a 1920 pixel monitor? If not, that's your answer.

Also (at least with FCE), you need to set the viewer to 100% before you choose full-screen display, otherwise you don't get full resolution...

Yes, FCE converts the HDV to AIC, but it should not really be perceptible. I've got great results, even saving from FCE to m2t and exporting back to HDV tape.

[blondandfun]

Are you basically telling me that there is no loss in image quality in the captured video in Final Cut compared to the raw data from my HDV tape using my current capture method? That basically, I'm seeing an image quality loss solely from my Mac to my HDTV as opposed the HV40 to my HDTV?

If this is your message - that the image quality loss is purely perceptual and that a Mac is unable to display the image quality on an HDTV that an HV40 can, and tha my current capture method is as good as it can be - then please let me know. Thanks.

What I'm telling you, is that it's stupid to assume otherwise

[blondandfun]

does it have a 1920 pixel monitor? If not, that's your answer.

What about the LCD on the HV's? Many people say it's in a way brighter and better than on computer.

Like I said you people need to stop thinking one-dimensionally. There's more to all this than your narrow minded knowledge of "resolution, color, and contrast" This is NOT photography, video technology is much more complex than this simple mindedness.

[jimbills]

B&F, why so hostile?

Jimbills: Are you watching the footage in full HD res on your computer, i.e. does it have a 1920 pixel monitor? If not, that's your answer.

Also (at least with FCE), you need to set the viewer to 100% before you choose full-screen display, otherwise you don't get full resolution...

Hi. And thanks. My HDTV is 720p - so the feed from both my Mac and HV40 displays the image on the HDTV as 1280 x 720, even though I am aiming to end up with a 1920 x 1080 exported video.

If the image quality loss is purely perceptual - that the Firewire capture method delivers 100% image quality from the HDV tape and that the image quality problems are strictly related to my Mac displaying the captured video on my HDTV - that is an answer to my question. Is this so?

Thanks, and thanks for being civil.

[Janke]

B&F: Note that Jim said: "I know the difference between contrast and brightness vs. image sharpness, color, and noise." He knows that from still photography. Also, many people complain that the LCD on the camera gives a false impression of the recorded result - I for instance, never trust the LCD to give me an indication of exposure - my Zebra is on, all the time...

We (all?) know that a Mac screen doesn't have the brightness and contrast of a TV, but as I understand it, the question is about resolution, nothing else here...

[jimbills]

What about the LCD on the HV's? Many people say it's in a way brighter and better than on computer.

Like I said you people need to stop thinking one-dimensionally. There's more to all this than your narrow minded knowledge of "resolution, color, and contrast" This is NOT photography, video technology is much more complex than this simple mindedness.

Hi. I'm not talking about the LCD.

Video is simply photography displayed with a time dimension. Each individual frame is a photograph.

And I do understand that there is much involved with video technology. There is a lot I do not know, and that is why I am here asking this particular question.

[Janke]

I've never connected a TV to my Mac's video output, so I can't say if you're supposed to get a different result - what I do know, is that Mac's use a 1.8 gamma, while TV's use 2.2 or 2.5 - much contrastier. If the HV camera can tell the TV to use 2.5 gamma, and your Mac tells it to use 1.8, you get a contrast difference, but the resolution should still be the same. Perceptual sharpness of course looks higher with a higher contrast...

[jimbills]

What I'm telling you, is that it's stupid to assume otherwise

Thank you for clarifying, and for proving the falsity of the saying, "The only stupid question is the one not asked".

[jimbills]

I've never connected a TV to my Mac's video output, so I can't say if you're supposed to get a different result - what I do know, is that Mac's use a 1.8 gamma, while TV's use 2.2 or 2.5 - much contrastier. If the HV camera can tell the TV to use 2.5 gamma, and your Mac tells it to use 1.8, you get a contrast difference, but the resolution should still be the same. Perceptual sharpness of course looks higher with a higher contrast...

Hi Janke, thanks - but it's not contrast. I'm very, very familiar with contrast - you'll just have to trust me on this. It's image sharpness and noise. I happen to have shot a low light situation. The noise exists in the video from the HDV tape in the HV40 to the HDTV - it's much more pronounced in the captured feed in Final Cut. Also, the image is sharper on a detail level in the HV40 to HDTV vs. the capture in Final Cut to the HDTV.

[blondandfun]

is the HDMI to TV interlaced or progressive?

How about the computer to TV? I think not on latter, but not sure about 1st.

That's one of a dozen other things you have to put into your equation.

[jimbills]

is the HDMI to TV interlaced or progressive?

How about the computer to TV? I think not on latter, but not sure about 1st.

That's one of a dozen other things you have to put into your equation.

The HV40 is set to 1080i in output. The Mac simply has a DVI-I connection which has an HDMi to DVI connector attached to an HDMI cable going to the TV. The TV itself is 720p. Beyond that, I don't know.

But again, it's why I'm asking. I don't know.

[cgbier]

Doesn't AIC downrez your picture to 960x540 for faster watching? I meant to have read that. That might be your answer.

[Janke]

Doesn't AIC downrez your picture to 960x540 for faster watching? I meant to have read that. That might be your answer.

It doesn't appear so, at least in FCE at the settings I have. Watching a scene in full-screen (1080 by 1920), I can see the interlace combing, line-by-line, so no downsizing there. (I'm talking about fully rendered scenes, here.)

YES, AIC has a default size as you mention, it sometimes comes up in the export dialog box, but I always export to full HD specs.

[Janke]

The HV40 is set to 1080i in output. The Mac simply has a DVI-I connection which has an HDMi to DVI connector attached to an HDMI cable going to the TV. The TV itself is 720p.

Are you mirroring the Mac's display onto the TV? Then the resolution is the same as on the Mac screen, and if that's lower than 1280x720, then you have your answer there...

[cgbier]

YES, AIC has a default size as you mention, it sometimes comes up in the export dialog box, but I always export to full HD specs.

If I'm not mistaken then Jimbills mentions the preview in FC BEFORE exporting in the original post. Therefore, AIC's downrezzing should be the problem.

I doubt you'll see a difference after rendering (depending on codec of course).

[iThinkergoiMac]

I've never had AIC down-rez on me before (not with iMovie 09, FCE 3, or FCP 5). When I open up files from import, it's still 1440x1080. I've actually never heard of AIC automatically down-rezzing like that before... maybe it creates a preview of that size? I find it hard to believe that it would do that.

@Janke: For what it's worth, Snow Leopard does default to a 2.2 Gamma setting. You're right about 1.8 gamma for everything before Snow Leopard.

@jimbills: Despite B&F's blatant lack of civility, he's mostly right in terms of the point he's trying to convey. The difference is simply perceptual. If I hook my HV20 up to my parents' HD Trinitron, it looks a lot better. It's just simply because the TV with the HV20 combined make the footage look better. I don't really know the technical details of why, though. It's not just the TV, and it's not just the HV.

With some color correction and enhancing filters in FCP, you should be fine. FireWire does transfer all of the information from the tape, same as the HDMI (though it does convert it to square pixels and a 4:2:2 color space before sending to the TV).

[jimbills]

I've never had AIC down-rez on me before (not with iMovie 09, FCE 3, or FCP 5). When I open up files from import, it's still 1440x1080. I've actually never heard of AIC automatically down-rezzing like that before... maybe it creates a preview of that size? I find it hard to believe that it would do that.

@Janke: For what it's worth, Snow Leopard does default to a 2.2 Gamma setting. You're right about 1.8 gamma for everything before Snow Leopard.

@jimbills: Despite B&F's blatant lack of civility, he's mostly right in terms of the point he's trying to convey. The difference is simply perceptual. If I hook my HV20 up to my parents' HD Trinitron, it looks a lot better. It's just simply because the TV with the HV20 combined make the footage look better. I don't really know the technical details of why, though. It's not just the TV, and it's not just the HV.

With some color correction and enhancing filters in FCP, you should be fine. FireWire does transfer all of the information from the tape, same as the HDMI (though it does convert it to square pixels and a 4:2:2 color space before sending to the TV).

Hi. Okay, thanks. I seem to have three answers that the issue is perceptual. I've thought about exporting the video back to tape and viewing it again - even though there would be a generational loss there, it might be interesting.

I have a follow-up question. When I was trying to figure this out in Google searches, I read all about Firewire capture. Obviously, the main advantage there is live capture. But, would an HDMI capture from an HDV tape have any quality difference from a Firewire capture from an HDV tape?

Again, that's probably been asked a million times, but I haven't found a clear answer. The BlackMagic website seems to imply that it would have a quality difference, but I'm wondering if that is just marketing.

Thanks again.

To cgbier: As far as AIC down-rezzing for display, I don't know. That would explain a loss in sharpness and increase in noise - I'll look into that. But, I have exported the video into a Quicktime .mov file using the best quality settings - and I don't see a major quality difference between the export and the scene viewed before export in Final Cut (at least, not as much of a difference as compared to seeing the video from an HDMI playback onto the HDTV).

To Janke: It's not mirrored. The HDTV is my only monitor for that Mac. Thanks again for your help.

[iThinkergoiMac]

I have a follow-up question. When I was trying to figure this out in Google searches, I read all about Firewire capture. Obviously, the main advantage there is live capture. But, would an HDMI capture from an HDV tape have any quality difference from a Firewire capture from an HDV tape?

The only time capturing via HDMI makes a quality difference is when capturing live. Once it's on the tape, HDMI vs FireWire makes no difference.

[jimbills]

The only time capturing via HDMI makes a quality difference is when capturing live. Once it's on the tape, HDMI vs FireWire makes no difference.

Okay, and thanks again.