Variable Video Picture Quality

[hoodwoods]

Hi. I am making DVDs using Vegas 4.0. I am panning and croppng pictures for motion effects and have some problems with shimmer of the images during crossover transitions. I am also a little confused about why the DVD looks great on my laptop but varies so much when you play it on TV's, HDTV's and such...help !

[guns1inger]

The most likely cause of the difference in viewing quality is that your laptop is resolutely progressive, however your TVs will be interlaced (CRT) or progressive but receiving an interlaced signal from the DVD player (HDTV).

Any photos with small patterns, horizontal lines etc. can cause shimmer on interlaced displayed, especially if you are zooming as you pan. You can smooth some of this out be applying a slight blur to your footage.

The other thing to remember with your HDTV is that you are at the mercy of your upscaler (player or TV) when playing back DVDs, and the quality can vary greatly from disc to disc.

[hoodwoods]

Thanks gunslinger. I was hoping not to have to blurr it up but if that is the only way ... as for the crappy quality issue...is there nothing I can do to get some sort of standard ?

[guns1inger]

The blur does not need ot be much. Even a slight directional blur can make a difference.

As for the quality - without a sample it is difficult to see what the problem may be. It is unusual for the quality to a single disc to vary greatly from TV to TV. As I said, upscalers can vary greatly in quality, with cheap players and cheap HDTVs having very poor upscalers. Regardless, this is entirely outside your control. The best you can do is make the best quality disc that you can. After that there is little you can do.

[hoodwoods]

Hi GS, The big difference in quality is in contrasting and clarity. Contrasting I am not worried about but i was with the clarity. I thought it may be due to TV variability but wasnt sure. I am selling DVDs so they get played on a lot of different setup situations and was wondering if there were special output settings which would be a magic cure and allow a quality pic to be seen across the board. once again cheers.

[guns1inger]

No magic bullet. Use the highest bitrate you can afford to use (i.e. do not use the default settings in Vegas), and make sure you use an authoring tool that does not re-encode your video at any point.

[vhelp]

Quality (or results) are varying for different reasons.

Some software players use their own built-in decoders for processing the video and finally sending it to your computer monitor. But even if you miss that, (in the case of an HDTV) they might have poor hardware pre-filtering features. And this could turn your opinion in another direction.

But what partly drives this is the given video format, ie: mpeg2 vs. h264 vs other format.

In most HDTV sets and LCD monitors, etc., these viewing devices have built-in filter enginges, including upscalers. Everybody is competing as the best quality.

Oh, and don't forget that all this applies to graphics cards as well. They have their share of hardware assistance, from video decoding to video (pre-filtering) processing, etc. And they are triggered also, according to the video type being sent, be it an MPEG-2 (for sure) and/or H264, etc.

As such, some formats may trigger the videos hardware to engage and begin pre-filtering the input video source. When that happens you are at the mercy of that tv's quality level. And that can be good or bad depending on the input video source you are sending. If the video is heavily filtered by you (via software, etc) then expect over-samping/filtering on the other end. VHS -to- DVD suffers greatly in this respect because this is an medium that gets heavily filtered by users trying to remove the amount of noise found in this already limited medium.

The reason why most MPEG-2 sources (ie: DVD and digital cable/satellite/hdtv) look better is because this source is already clean and consequentially doesn't go through much user-pre-filtering applications. So they tend to look fairely good. But you still have to worry a little with the upsampling capaiblities of the viewing devices. There are good and there are bad upsamplers.

So, you are prob best to experiment when you encode video for a given platform/medium. Try encoding a video with and without filtering applied. See how each video is presented in your given viewing device, be it an HDTV or LDC monitor.

A good example of this nonsense is like this:

I have an MPEG-2 I encoded. When I play it in windows media player, my ATI Radeon HD 3450 graphics card detects it as an mpeg-2 and triggers certain hardware assistanced features. One of them is the MPEG-2 decoder engine, but can you guess what the other is ? Ok. I see you figure wrong. Let me correct you. It also triggers the hardware assist pre-filter. So now my mpegs look all masky looking on my new 19" monitor. Well, it not very good this way. But then, my mpeg-2's origin stems from my analog (dv) captures from my noisy analog cable tv. So, yeah, I do a little filtering, but not much. But, its enough to make them look like sh_t against a good ATI card just mentioned and a 19" widescreen monitor using the VGA connection.

Now, using the same encoded video source mentioned above, but this time, using VLC player, things are a bit different. The quality is MUCH better and enjoyable!! Because the hardware assisted pre-filter did not get activated, so my video played with perfect quality as I designed it to be. It was perfect.

But to be clear, the reason the HD 3450 hardware assist kicked in was because the ATI and software driver were designed to operate that way with each other and windows media player when all the variables add up correctly.

So, I say, Test Test Test ... before going off the deep end.

-vhelp 4930

[hoodwoods]

Thanks team. Will be back sometime in the future with more probs no doubt or maybe just the same ones unresolved....cheers alround.