Quality of images (jpegs) in finished DVD

AlanADale wrote on 8/21/2011, 12:16 PM
For the first time, I recently imported into a project still jpeg images along with video clips. The resultant project was then rendered in two stages - mpeg2 and ac3 - for import into DVDA (PAL widescreen) for completion and burning to DVD. A wide screen PAL setting was also selecting in VMSP by the way.

Whilst I am overall pleased with the resultant DVD (the video is great), I am greatly disappointed with the quality of the still jpeg format images which are both unsharp and demonstrate a lot of pixelation. The still images are shot in raw format using my Canon 7D producing 18MB files. These are edited in Adobe Photoshop with the shots for inclusion in my video project being shot to allow for cropping into a 16:9 size thereby negating my having to use the Pan/Crop tool. The images are exported from Photoshop as jpeg images at the maximum quality setting usually producing files in the 6-8MB range. These still images look good in all photo viewers even when at full screen size but fall down miserably when they finally end up on DVD.

Now I realise that the jpeg format is a compressed format and that I undoubtedly will be losing some quality once again when further compressed to a format for DVD. That said I wouldn't have expected the drop in quality to have been quite so bad, so my question really comes down to...........is this normal and to be expected? From the supported formats information I see that the only other choice would be exporting the images as PNG's so the second part of my question is does anyone have any experience in having tried this and what were the results like? Thanks..

Comments

Tim L wrote on 8/21/2011, 1:37 PM
A PAL DVD has only 720w x 576h pixels. When your 18 megapixel stills are put into PAL DVD format, you end up with an image that is roughly the equivalent of only about 0.4 megapixel resolution. (Don't feel too bad -- the resolution is even lower than that for those of us in NTSC land.)

Without us seeing the actual images that you are seeing, it might be that the quality loss you are seeing is simply the loss of resolution. Your 5184 x 3456 originals are being converted down to 720 x 576 pixels.

To further complicate things, the 720w x 576h pixels are not square pixels -- they are rectangular. The vertical value is the same as the number of visible scanlines on a standard definition TV, then the horizontal part of the image -- whether 16:9 widescreen or 4:3 -- is simply divided into 720 pixels. So a single pixel on a PAL DVD is about 1.45 times as wide as it is high.

http://en.wikipedia.org/wiki/Standard-definition_television

The roughly equivalent "square pixel" format in a photo editing program would be 1048×576. In photoshop, try saving a copy of your image as 1048×576, and see if it exhibits the kind of detail loss you see within Vegas. The video format -- being only 720 pixels across -- will actually show even less horizontal detail.

You only alternative -- assuming you are playing this video to a high def TV -- would be to go to 1920x1080 Blu-ray disc or a similar format that you could play from a USB thumb drive or media server.

If playing from a laptop -- maybe with an LCD projector? -- you might have higher resolutions available.

Regarding JPG vs PNG: I haven't done any direct quality comparisons, but I generally just use PNG anyways. PNG (portable network graphics) is very widely supported now, and has the advantage of being lossless -- no loss of data whatsoever when saving an image -- and also supporting alpha channels -- so your image can have transparent areas.

http://en.wikipedia.org/wiki/Portable_Network_Graphics

Ooops! One more thing: when using still photos that must be resized for your final video output, be sure to set your Full Resolution Rendering Quality to "Best" (in your Project Properties). This setting will improve the quality of high-pixel-count images that are downsized to video resolution.

Another option -- which will make editing a little zippier as well -- is to resize the photos outside of Vegas so that the image you bring into the project are probably no more than double the project resolution in each dimension. For example, use photos that are already resized to no more than 1000 or so pixels high if doing a Std Def PAL DVD. If you aren't zooming too deeping into the images, maybe only 600 - 700 pixels high.
AlanADale wrote on 8/22/2011, 12:46 AM
Many thanks for that very detailed and informative response Tim L - much appreciated. My PC (with DVD burner) is due for replacement in a few months time and I guess it's now time to think about the inclusion of a Blue-ray compatible drive and at the same time invest in a Blue-ray player. Whilst I have a high def TV the USB socket will only play back jpeg still images and not films. I am, however, able to attach my Laptop so will also give that idea a try.
Thanks again.