How DVD players give both NTSC and PAL o/p from a NTSC DVD

[K. S. Amar]

I have a DVD player which can give a PAL or NTSC ouput while playing a NTSC DVD. The converse is also true (ie., a NTSC o/p while playing a PAL DVD).

How is it possible?. The aspect ratio is also fine and the jerks in video is quite tolerable.

I need this info because it wil help me in my work. I am into developing MPEG 2 content for set top boxes.

[bugster]

The aspect ratio is also fine and the jerks in video is quite tolerable.

The only parts of a DVD that are NTSC or PAL specific are the framerate and the resolution. Resizing is relativley straight forward but as you noticed the framerate conversion can cause slightly jerky playback.

[chicola]

http://www.michaeldvd.com.au/Articles/PALvsNTSC/PALvsNTSC.asp

Basically, what's recorded in the DVD is a specific digital data stream.

The player electronics output the analog video timings dependent on the type of video system selected (NTSC or PAL). That is done during the DIGITAL-> ANALOG process.

If you already had a analog signal (and wanted to convert it from NTSC to PAL, for example) then the usual way is to use a scan converter. Essentially, an NTSC color decoder/A-D feeds a frame buffer (approximately VGA size). The frame buffer is then read out at PAL rates and the necessary interpolation is performed using digital processing to go from 525 (480 or so active) to 625 (580 or so active) lines. The output is sent to a video DAC and then color encoded for the PAL system. Everything all happens in real-time.