The quality of a video signal depends on:
That, we can do very little
- The encoding/mastering quality of the DVD
This is in fact quite important, and quality does seems to differ from region to region. We can see that the disc imported from (south-east) asia are occasionally poorly mastered & encoded. Disk we can buy in the states are usually of good quality.
- The production quality of the DVD
If it's scratched, the reflection layer not nice enough, there can be problems reading the disc, resulting in stuttering, mosaic formation and so on. This also put a stress on the laser reader because higher power is often needed to re-read the disc multiple times, decreasing the lifespan of the laser. A normal read-out in a PC at the speed of the DVD drives practically preclude quality of DVD as a reason of problems in DVD visual/audio quality
- Quality of the DVD transport
Most DVD transport are good enough nowadays
- Quality of the audio and visual DAC (whether on DVD player, receiver or display panel)
The DAC is where the digital signal transformed into the analog signal, thus, if you use digital interconnects, that would be the last piece of equipment (i.e. the panel).
If you use analog interconnects, that is where the analog interconnect starts.
DACs vary in quality and cost (a lot). In general, high quality (e.g. 24/192, >100dB dynamic range for audio) DAC are found in most audiophile grade equipments, as well as personal computer with a standalone sound card. All display card nowadays contain excellent quality DACs
- Quality of the transfer cable
For analogue interconnects, think about the (1) inductive, (2) capacitive and (3) resistive quality of the cable. For short runs (less than 2 meters), even for unbalanced, poorly made thin cable would have no audible effect on audio signals (i.e. Less disturbance to your audio signals of 20kHz bandwidth than your equipment's noise ground for most places)
For digital interconnects, if the interconnect satisfies the standard (i.e. Bandwidth/LCR parameters) then it will just work. Pay attention to the specification rather than price of the cable. A $10 dual-link DVI will be able to do a 2560x1440 screen whereas a $500 HDMI cable could have a little problem.
This is quite often where people leave out. LCD is the most common type of display nowadays, and we need to think about
1) The backlight
In general, RGB LED > Good CCFL > White LED ~ Average CCFL > Bad CCFL
2) The LCD technology
TN - fair viewangle, good response time (can be as low as 2ms GTG), 6bit color/channel
IPS - almost the best viewangle (178/178 degrees), fair response time, 8bit color/channel; Note that there are different types of IPS there.
MVA/PVA... - those are different technologies based on VA (vertical alignment) mother technology originally designed to be a compromise between TN and IPS. These have now evolved to have similar quality to IPS panels.
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