HMC 151 HDMI live feed output

M

Mort

Member
Hi Folks, I did a test today using the hdmi output from the camera direct into a 50inch Panasonic plasma screen and then I recorded the same scene and compared the two. ie switching from live feed to recorded image of the same scene. Looking at the image at point blank range I couldn't see any difference between the two even when zooming the image on the screen, why would this be? I would expect a disparity between the two, or is the hdmi feed already proceesed on this camera, any thoughts?
All the best Mort.
 
Hey Mort,
It is my understanding that the live HDMI signal and the recorded AVCHD image look extremely similar. I think that's a testament to the quality of AVCHD. You can get a great image in a really small, compressed h.264 file. The problem is that there is less information so if you want to adjust the image in post production the NLE or color grading software is going to have a more difficult time "manipulating" the image. I believe that's why h.264 compressed files have often been used as a delivery format where as the format the footage is captured on is much more uncompressed. Avatar may look great on an blu-ray disc that has h.264 compression but the initial "camera footage" was much larger and very uncompressed with a 4:4:4 color space.
 
Hi Richard, this is going to sound stupid but, I did another test today different subject. Looking at the live feed from the hdmi it does look slightly different from the recorded hdmi output but only at a pixel level. It's odd but there appears to be more noise on the live feed hdmi than on the playback hdmi. It this because the the codec is not recording the subtle noise that the live feed is showing?
Any thoughts Richard or anyone?
Many thanks Mort
 
The codec has to lose something in oder to compress things enough to fit - and often the only thing it can do is smooth out some noise ;)

HDMI and AVCHD look very similar, but then they would have to or people would complain about how bad AVCHD was ;)

Unless I'm keying, I don't see enough difference to use the HDMI out over AVCHD.
 
Hi Exact, thankyou for your response here. Cards on the table, what I'm trying to do is decide if the Pany footage would benefit from a Nano or Ninja. I'm trying to squeeze as much image quality as possble out of this little camera but I suppose in the end there is no substitute for resolution. I do really like the camera though and even though my Canon 5d shoots video, I still prefer the quality of the Pany.
 
Technically yes, you're going to get more data from the HDMI port than the AVCHD codec will record. Namely, 4:2:2 color space. If you're green-screening that could be a big deal.
 
Have you guys ever compared an HVX 200 live feed to the HMC 151? My friend has the HVX200 and we did a back to back comparison between the two cameras recording. We transcoded identicle footage to 422HQ and compared. As far as I could see the HVX200 was cleaner in the light/mid tone areas and only more noisy in the dark areas, but overall in a daylight situation the HVX200 looked cleaner, I felt.
A Panasonic rep said to me that the HMC sensor is the same as the HVX, he said that the data compression is what made the image differ, but this has to be wrong, because where is the noise coming from on the HMC in the highlight areas (ie the Sky) that is absent from the HVX200?
Is it the codec or is it sensor noise? I always assumed the overall noise on the HMC was the codec, but now it's starting to seem as if it were noise from the sensor. What do you guys recon?
Sorry to be a pain guys, I'm just trying to work out how much gain in quality I will get from a remote recorder, but I guess the only way to really know is to do it and compare. ;-)
 
The HVX200's sensor is different from the HMC150. The HVX200A's sensor is the same as the HMC150. So you'd have to know if your friend had a 200A or a 200, to know if they were comparable.

Even though they're the same sensor, they're not exactly the same imaging chain, and an HVX200A doesn't produce images that look identical to the HMC150.
 
Hi Barry, so as I pixel peep at the footage from the HMC 151, the very fine noise I'm seeing is that mainly sensor noise as apposed to codec noise? Also do you think it's worth running this camera through a Ninja 422HQ recorder ie will I improve at all on the colours and tone or resolution? TigerFX says its mainly useful if your keying, but I don't do much of that. :-)
 
I doubt going into any of those 8-bit recorders will help your colors look better - the advantage is in the increased latitude for grading.
 
Ninja doesn't exist, Ki Pro Mini isn't on the market yet, so that leaves the Nano, which costs as much or more than the HMC150. So in summary -- no, don't bother.

Secondly, AVCCAM is really quite good, and the HMC150 isn't going to put out so much resolution as to seriously challenge the codec.

If you're seeing noise, you should just adjust your scene file settings to weed it out, rather than looking at alternatives like external recorders. Turn down the detail level, turn up the coring, use b.press, and maybe norm2 or fluo matrix, do a black balance, drop the master pedestal a few notches... you can make lots of noise disappear doing those things.
 
Wow, great advice chaps and thankyou for your time. I shall try those settings and yes I'm really glad I got this camera, just looking for how to get the max out of it. I will bin the Nano idea now.
Many thanks folks, all the best, Mort.
 
The Nano's great, by the way. I'm just saying -- work with what you've got before you decide you need to buy something else. If you need high-bitrate 4:2:2 intraframe, the Nano is an excellent option. Just be sure you need it, before you buy anything additional, that's all.
 
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