resolution

[byair74]

Hi,

I understanding that TV PAL resolution is 576x520 and VHS PAL resolution is only 576×310.
so, when VHS tape play the frame is stretch to 576x520?

thanks,

[Ai Haibara]

Your TV is probably automatically scaling it. Do you have any options on the TV to make sure everything's displayed in its proper (original) resolution and aspect ratio?

[byair74]

thanks, for the quick answer but I waiting for a more confident answer, by the way this is the same on NTSC.

[hech54]

thanks, for the quick answer but I waiting for a more confident answer, by the way this is the same on NTSC.

I'm still trying to figure out where you got these numbers from?

I understanding that TV PAL resolution is 576x520 and VHS PAL resolution is only 576×310.

so, when VHS tape play the frame is stretch to 576x520?

[videopoo]

Lol. Yeah.....we need a confident question before there can be a confident answer

[byair74]

Hi, you can find this numbers in the following Wikipedia articles.

http://en.wikipedia.org/wiki/List_of_common_resolutions?#Television

thanks,

[edDV]

Hi,

I understanding that TV PAL resolution is 576x520 and VHS PAL resolution is only 576×310.
so, when VHS tape play the frame is stretch to 576x520?

thanks,

Not quite.

Analog PAL has 625 horizontal lines total, 576 in the active screen area. Since it is analog, there are no horizontal pixels. Horizontal resolution is expressed in bandwidth. PAL broadcast has ~ 5 MHz bandwidth, VHS is limited to ~3 MHz but records all 576 lines.

DVB SD digital broadcast uses 704x576 pixels. DVD uses 720x576 or 704x576 pixels*.

When you play analog video to an HDTV, the input video is sampled @ 13.5 Ms/s to 704 horizontal pixels. The 704x576 frame is then upscaled to screen resolution.


* Additional smaller resolutions can be used for DVD such as 352x576 or 352x288. See all allowed resolutions in "What is DVD?" upper left.

[byair74]

1st, thanks all

so, analog video can sampled to different resolutions without losing quality?

[edDV]

1st, thanks all

so, analog video can sampled to different resolutions without losing quality?

No. Smaller frames will have lower quality but it may not make a difference if the source video is low quality.

For example assume a high quality SD studio camera that has 8 MHz horizontal resolution.

If that camera signal is sampled at 13.5 Ms/s, effective bandwidth (e.g. for DVB broadcast or DVD) is reduced to 13.5/2 = 6.75 MHz. This corresponds to a 704x576 frame.

Note that 13.5 Ms/s is more than enough for PAL broadcast or VHS.

To get to 352x576, the 704 samples per line are filtered down to 352 if done correctly. If one just deleted every other pixel, there would be edge distortion problems when the player stretched 352 back to 704 for display. 352x576 is almost enough to contain VHS in a perfect world but noise and other recording issues cause artifacts unless the captured signal is noise reduced and low pass filtered before encoding. If maximum quality is the goal, you need to encode to 704 or 720x576 because DVD offers no options in between.

If DVD is not the goal then you can encode to other resolutions. Many cable or satellite systems reduce sample rate to fit more channels. Typical frame sizes range from 524x576 up to 640x576 to achieve SD "cable quality". These resolutions are resampled (stretched out) to 704x576 in the cable box or satellite tuner before export to HDMI.

[byair74]

thanks, edDV