CurtPalme.com Home Theater Forum

[AnalogRocks]

Anybody know of a good bandwidth calculator to calculate the MHz?

Eg if we had 1024x768 @ 120 MHz how many MHz does that equal in terms of HDMI bandwidth?

How do you calculate this?

[AnalogRocks]

Anybody know of a good bandwidth calculator to calculate the MHz?

Eg if we had 1024x768 @ 120 MHz how many MHz does that equal in terms of HDMI bandwidth?

How do you calculate this?

[Nashou66]

Well this isn't a bandwidth calculator per se but with it you can add in all the data and it will tell you what the pixel clock is. its the resolution editor for the Tv-one scalers. its how you can add custom resolutions to your scaler.

Since just resolution isn't the only determining factor of bandwidth( timing numbers change the pixel clock as well) this is a good tool.

http://files.me.com/nashou.66/dv86rn


So according to your resolution its about 139 Mhz pixel clock using the above program. the pixel clock info is in the Advanced create & edit Resolution tab.

Athanasios

[VideoGrabber]

AR inquired:
> Eg if we had 1024x768 @ 120 MHz how many... <

I think you meant 120 Hz there, not MHz.

> ...how many MHz does that equal in terms of HDMI bandwidth? How do you calculate this? <

What do you want this for? I.e., your question is a bit confusing, because HDMI is a digital signal (you know, bits), and thus is normally reported in aggregated GBit/sec terms (though that's called bandwidth as well, just not in MHz terms). It also breaks down into the full TDMS bandwidth (bitrate), and the video bitrate, and audio bitrate components. So I'm not sure which number(s) you're looking for.

[In case you're wondering, the audio component doesn't expand the bit counts because it's cleverly stashed in the blanking intervals in the video signal.]

You can relate the full TDMS bandwidth back to the analog bandwidth (pixel clock) necessary to carry the digital signal, if you like, which you can get roughly by dividing by 30. E.g., HDMI 1.2 maxes out at 4.95 GBit/sec == 165 MHz. Not coincidentally, each pixel has 3 channels of data, with 8 data bits + 2 overhead bits per pixel for the coding.

In general though, it's pretty simple:

....HDMI bitrate = (horzPixels + hBlanking) x (vertPixels + vBlanking) x bitsPerPixel x frameRate x 10/8 (for TDMS encoding).

The first 2 components combine into the frame size, the third adds depth, the fourth the temporal component, and the last the transmission mechanism overhead.

[AnalogRocks]

[AnalogRocks]

[cinema mad]

That is an Excellent Resolution Calc Athan Thanks for sharing,


Cheers...

[VideoGrabber]

> The reason I'm asking is because someone wanted to know if the HDFury2 will handle 1024x768 @ 120Hz. <

Ah, OK. I have no idea how it will respond to that frame-rate, but I can say it will not be bandwidth (or bit-rate) limited with that signal. Your PJ may not be thrilled with a 100 kHz hScan rate though (that's close to the limit for many PJs, and in my limited experience, PJs frequently don't operate as well when pushed to their limits).

> I need to know how to calculate the equivalent in MHz as it pertains to the HDMI signal. <

To know precisely, you'd need the vBlanking and hBlanking specs for 1024x768, and I don't have the HDMI spec here. It's what dictates the timing for the various resolutions. But even if you used the 1920x1080 blanking intervals (too large), you'd still be under 130 MHz.

The rez calculator that Nash provided imposes larger, analog-style porches, which are wider than needed for digital signals, but may actually be more appropriate for a CRT. That utility reports almost 140 MHz.

Just doing a back-of-the napkin type calculation, you know that if it handles 1920x1080x60p (which it does), ignoring the blanking means that your suggested 1024x768x120 uses <80% of that capacity. So, anyway you slice it, it's less than the 165 MHz HDMI bandwidth on the HDFury2.

[HKmod]

This one should please you : http://www.epanorama.net/faq/vga2rgb/calc.html