TMPGenc: output YUV as CCIR601.......mistake

[davefx]

hate to drag this up YET AGAIN, but it seems i have made an error regarding this checkbox.

when i first started recording/encoding i was using an ATI card. everything went fairly smooth minus the typical sync issues which i worked around. when encoding the resultant AVI files in TMPGenc, i UNCHECKED the "output as....CCIR601" box as per understanding from reading here. all went well, never thought about it again.

as time went by i upgraded to DV/firewire input for recording. about 6 months have gone by since then, and after relearning a lot of things in terms of encoding, color correction etc i have found i now had this box unchecked in error.

all of my DV material encoded to DVD looks like it has a white sheen over it. black is gray when viewed on NTSC tv, contrast is off. this is the last problem i have tackled and it went unnoticed because i had quite a few more issues to work out before zeroing in on this step.

as i became better at setting the encoder for the material (i find this is extrememly important; different material = different settings) i began to compare the DVD's made from the ATI card against the DVDs made from the DV source. the ATI card source DVDs have the same color, contrast, brightness as the original ATI AVI's. the DV source DVDs do NOT look like the original DV files.

so i read some more here, and zero in on this mysterious box called "output yuv........CCIR601" and determine that for DV files i need the box CHECKED. oops. my bad.

so i quick captured some tv over firewire and make a few dvds with the box checked. low and behold, the resultant mpeg2 file looks like the DV file, and looks like the broadcast does when i play the dvd on the tv. why this took so many months to figure out.......lets just say i'm still learning about all this....

my question is (and i fear i already know the answer).....

can i take my INCORRECTLY encoded mpeg2 files (checkbox unchecked) and correct this mistake somehow by re-encoding them? i kind of doubt it, and its not critical or anything, but i have a number of dvds that would be much more enjoyable if they were corrected.

mostly i ask because, lets say i have a season of tv shows on various dvds, some of which look right, and some of which look wrong. i'd like to make them all look right.

at least now i know how to set the box for my material i work with(!!!)

please dont turn this thread into yet another arguement about how to set the checkbox. only about how to reverse the error or checking the box incorrectly.

[vhelp]

Yes. This has ben discussed pretty exhaustively. Anyways.

Here is a link to what I beleive it the best answer(s) to your
issues w/ this feature and TMPGenc.

- TMPGEnc CCIR601 option REVEALED!

-vhelp 3028

[lordsmurf]

With DV, yes, that's an understanding. Some 411 filters are also needed if you're NTSC.

[adam]

Yes you can fix it. By improperly unchecking this option your levels were compressed moreso then they needed to be, but all the information is still there. Nothing was clipped.

You need to frameserve them through either virtualdub or Avisynth before going to TMPGenc. Use a levels filter (you can see how to use the one in Vdub in the link that vhelp posted.) I would expand my luminence ranges so that it was in the 0-255 range. Basically, find a scene with clear black and white and pull the outer sliders in so that they just border the outer edges of your luminence graph.

Simply put, look at the two pictures in MrMoody's post in that link above. You want to make your graph look like the top image.

Then when you frameserve to TMPGenc you want to leave this option UNCHECKED. Since your source is now 0-255, unlike what your DV originally was, you do need to compress the luminence.

This should give you proper luminence levels in your encoded output, but of course you will have to live with the quality loss from doing another re-encode.

This is a long shot, but see if your dvd player has a true black or super black option. This will effectively correct your improper luminence levels without having to re-encode.

[andie41]

davefx,

You could re-encode your "incorrect" mpegs, use a filter to expand the luma, and check the "output as....CCIR601" box in TMPGenc. A lot of work.

As you have discovered, TMPGenc has compressed your luma - it was assuming 0-255 and adjusted these values to 16-235; however, as you probably already were at 16-235, TMPGenc compressed the luma to around 32-220. We are only dealing with IRE of 7.5 - relatively small amount, but noticeable. By adjusting the brightness/contrast of your TV, you can mask a fair bit- not perfect, but by far the easiest method.

Another scenario that I have had to deal with and may be applicable to you. I don't have cable so I can't test the video signals, but when I convert my analog NTSC tapes to DV, the avi's have black level at approx 32 (7.5 IRE) and white level at approx 235 (100 IRE). Excellent for watching on a standard NTSC TV.

If I use TMPGenc to encode, without checking the "output as....CCIR601", it compresses the black and the white levels, and thus my black level becomes around 48. Now when I burn to DVD and play in my standalone DVD player, it adds...7.5 IRE to the blacks, or what was once blacks. In this case, I would definitely re-encode.

[davefx]

thanks. i'm glad for the information. i will try to frameserve the mpeg2 files through VDUB and use a filter to re-expand the values and UNcheck the CCIR601 box.

i'm only going to attempt to fix my current run of tv shows, american chopper. i've got about 16 encoded wrong and 2 encoded right.

i did all 50 episodes of family guy off of adult swim and never noticed the problem; i guess cartoons are more forgiving even if they are a little off.

the american chopper program has had the highest learning curve to it yet for me. the quality of the broadcast is quite low, noisy, and often the reds in the program are waay off (too saturated). i suspect that they occasionally use a DV cam along with higher end cams as the color space/detail/quality changes quite often from episode to episode, and often within an episode.

i'm not doing this for the tv shows themselves. i'm trying to get this whole process to be second nature so i can work with amatuer footage eventually. i like the shows, but i end up never watching them once they are on the dvds. silly eh? i have about 40 some disks now.

still have a lot to read and learn. in two years of doing this, i still have never tried frameserving although i understand the concept. i'll give it a try!

[andie41]

adam,

After I wrote my previous comments, I saw your message and as you have previously stated, you are generaly thinking digital, and I am usually thinking analog. You suggested expanding the luma back out to 0-255 and I am thinking just get it to analog specs and keep it so.

I understand that the original luma data hasn't been discarded, but with the variety of encoders. decoders, filters, etc., will the luma be expanded back to its original state or just an approximation, depending on the software used.

[adam]

I don't know what you mean by analogue specs. Whether we measure in IRE or digital lumience, we ultimately want to digitize our blackest black at 16 and our whitest white at 235. Assuming we are looking at a scene that should have true black in it, and a scene that should have true white in it, we can easily set our luminence values exactly as they should be, which I would hope would coincide with how it was broadcasted.

I think you might be confusing IRE and digital luminence values a little because I see that you listed 7.5 IRE as being 32 on a digital luminence scale? That's not correct. A digital value of 16 is equal to 7.5IRE when converted to an NTSC analogue signal. That same digital 16 value is equal to 0 IRE when converted to a PAL analogue signal. The step-up associated with NTSC sources only exists in the analogue domain and has no effect on the digital source. Ultimately, ALL sources need to be digitized at 16-235. (some slight variation in certain regions but true generally) Once we get the video to our computer, analogue measurements are meaningless. As long as we are looking at the actual digital luminence levels, as opposed to say, trying to remember whether we digitized at 0 IRE or 7.5 IRE, then we can easily just adjust our levels to where they need to be.

[andie41]

What I meant by "analog specs" (perhaps incorrect terminology) was to get my luma to 16-235. I may very well be "confusing IRE and digital luminence values". I have worked out a practical method that gives me satisfactory results, but I wouldn't rule out the possibility that I am confused with the theory and/or technical aspect.

I mistated when I refered to IRE 7.5 as 32RGB; I was thinking about what happens to the black level in TMPGenc, if the "output as....CCIR601" box is not checked. However, my premise, I believe was correct, in that without checking the "output as....CCIR601" box, the black level will be raised and also, my DVD players kick it up another notch.

I am still curious as to whether expanding the luma will restore the values to their original state or will different software provide varying results. I guess my thinking is that I am skeptical of what the software is doing and the less I mess with it the better.

[adam]

Yes, leaving that option unchecked in TMPGenc will compress the luminence levels. That is why you can easily ensure proper levels simply by feeding it 0-255 sources. To get this you need only expand your luminence ranges to their outer levels in the last program in the chain before sending the signal to your encoder. Assuming you don't clip your values anywhere in the chain, the effect of all your software and codecs doesn't matter. Now excessive conversions between RGB and YUV are very bad, but strictly speaking of your levels, as long as nothing is clipped you can easily ensure proper levels in your final mpeg just by setting the encoder properly.

So, simply expand your luminence ranges to their outermost ranges in Vdub and frameserve to TMPGEnc with the option unchecked, and you can be guaranteed that your levels will be the same as they were at broadcast...again assuming you haven't clipped them at some point.

You could expand your ranges to 16-235 in Vdub as well, and uncheck the option in TMPGenc. Either way produces the same result, I just find the former option easier.

The amount that your dvd player "kicks it up" is just the step-up inherant in the conversion to an NTSC analogue signal. Its not something that you can, or should try, to take into consideration during encoding.

[andie41]

adam,

We have had this dance before and I don't want to hijack the thread, so a couple of comments and I will retire. As I stated, I have developed a method that appears to work quite well for me, perhaps I am confused with the technical aspect. If someone is copying analog to digital and having problems with black levels, perhaps my previous comments could be useful - perhaps not.

The amount that your dvd player "kicks it up" is just the step-up inherant in the conversion to an NTSC analogue signal. Its not something that you can, or should try, to take into consideration during encoding.

If I play my tape from camera to TV, looks good. Run through waveform monitor - black level 7.5. Transfer to DV on computer, encode with TMPGenc, check "output as....CCIR601" box to keep TMPGenc from compressing luma, burn DVD, play in DVD player - blacks don't look so good - run through waveform monitor and see black level is 15 IRE. I don't know what to say or think, other than if I don't take this into consideration, I don't get the reults I want.

Anyway, I will now go back to lurking ...

[adam]

Mpeg itself, as used in the DVD standard, only supports a maximum digital range of 16-235. Regardless of your source or playback hardware, you want the blackest black to be 16 and the whitest white to be 235 otherwise you are not maximizing the full luminence spectrum. This is something that is universal. You must ALWAYS do this when making a DVD. This is exactly what you are doing through whatever extra steps you are taking to achieve 7.5 IRE at playback. I'm telling you what the final result MUST be in all cases. You are just pointing out that sometimes you have to do various things to actually get to this point. I agree, but that's why I suggested that the original poster fix his levels at 0-255 in Vdub and then frameserve to TMPGenc with the YUV option unchecked. This should ensure that he reaches the proper 16-235 luminance range, just as you do through your own tried and true methods.

From the description you have given me, where your levels were off, I can tell with absolute certainty that you are feeding TMPGenc footage that is already compressed more than 16-235, and it is therefore impossible for you to properly calibrate your levels by that point through TMPGenc alone.

If the original poster follows the steps I have given, this will not happen.