quality of the output of BT878

[hans33]

With TV display/capture cards based on the BT878 chipset, such as the Hauppauge WinTV GO, I am interested in the actual quality of the output to the
1. video RAM for display on the overlay area
2. main RAM for saving to disk as the captured digitised (compressed) video.

Full PAL quality has been defined as 768x576pixels by 24bitcolour @ 25 frames/sec & 50 fields/sec, but for various reasons a little less than the 768x576pixels are actually used for the picture.

Is it the case that the cards (WinTV GO) work as follows:
1. the RF signal is recieved by the TV tuner and converted to analogue signals representing the picture and audio components of the video
2. the video analogue signal is sent to the BT878 chipset which digitises each horizontal scan line into
H pixels of C bit colour depth
3. the digitised video is sent to the video RAM for viewing or main RAM for capturing
4. the audio analogue signal is sent to the output jack, to be connected to the audio card which then digitises it.

Is the quality of the output signal from the TV tuner equivalent to full PAL quality?

What is the output from the BT878 chipset?
1. is it 768x576pixels 24bitcolour 25 frames/sec
2. is it 768x288pixels 24bitcolour 50 fields/sec
3. is it some lower resolution &/or colour depth

When selecting the resolution of the video for display or for capturing
1. is it the BT878 chipset which digitises to the selected resolution / colur depth or
2. is the output from the BT878 the same and the display / capture software converts this output to the selected resolution / colur depth?

[Anonymous65]

I don't know to much about the BT878 chip, but it can do 640x480 (640x576 PAL) and the color is 4:2:2, not 24 bit. To simplify, the color resolution is only half of the black/white resolution, both in the vertical plane and horizonal plane. I'm not sure the numbers are correct, but it's like the B/W image is 8 bit @ 640x480, and the color image is 4 bits @320x240. This all comes down to the NTSC/PAL TV standard, and that the human eye has only half the color resolution than black/white light.

Anyway, I do not believe that the BT878 chip can do DVD resolution of 720x480 (576).

SK

[hans33]

Hello

Thanks for your reply.

A previous reply on a related topic 'ATI TV WONDER - anyone capturing at 480 width???' was:
"The TV Wonder card is the same as the WinTV card, a $49 card. The card can do 640x480 with vidcap32 or virtualdub. Also, the 480 is the height in lines, not the width. 640 pixels wide by 480 pixels height." (which was also by you)

I was not sure what this meant and wondered if someone could clarify for me.

Did you mean that the TV Wonder and WinTV produce 640x480 quality (in PAL 768x576), or, that virtualdub will save
640x480 during a capture by using pixel doubling to enlarge a 320x240 image from the card?