BT601 / 656 PAL Video Buffer Size

can you just get away with using the active samples? from

Active video resolutions are either 720x486 (525/60videosystems) or720x576 (625/50videosystems).

martin

Oh Yes,

Data outside the 720x576 is fixed and known, and doesn't need sampled.

TA!

Regards Joe

Joe G (Home) wrote: > Hi All, >

As other have said, you don't need to sample the line and frame retrace but you need to double the memory if you want the color. There are 2

13.5MHz streams, 1 for luma and the other multiplexed for half-bandwidth R-Y and B-Y channels.

GG

Just remembered, 656 serial stuff is 10 bit, if you use just 8bit you save some memory, and 8 bit was good enough for "broadcast quality" for years

martin

Thanks Martin and Glenn,

My goal is to use a micro (connected to a SD card or larger serial flash mem) connected to a Averlogic dual port frame buffer (AL440) to drive a Philips SAA7128 / SAA7120 (composite video out).

The AL440 has an 8bit sequential in and out ports that can be clocked from the SAA7120 / SAA7128.

I am just trying to guage the memory size of the flash and AL440 for one complete frame.

I have access to these parts from Averlogic, Philips, and SST ... so I would like to use these.

I think I will need the to include the line and frame data as the AL440 data is clocked in sequentually.

Unless my software counts the end of a frame and send the line and frame info withing the code

Any other thoughts you have would be appreciated.

Regards Joe

Hi Joe, (please dont top post)

Those dreadfull philps data sheets, I tried to figure out if the SAA will generate sync pulses for you, and it can be used in Master mode, I think, check section 7.4 on the 7120. But the 7120 needs a parallel video data input, and you are using serial flash, seems a bit of a messy way to do it,

My brain hurts, need coffee

martin

Hi Martin,

My read up of the BT601 standard says you put the Synch pulses in the data stream and the BT656 is the parallel interface standard.... to transport the BT601 data. (obviously parallel is faster than serial and needs to be 13.5MHz, and serial would need to be 8 times this speed for 8bit).

The picture frame will be stored in memory (weather serial or parallel) and the micro is used as the mechanism by which the video data from flash is written to the video buffer. The output of the video buffer is 8bit parallel transmitted to the SAA712x.

The input side of the video buffer can be slow written data and the output side can be at full 13.5MHz.

I could use a parallel flash and a clocked CMOS 4040 to clock the address range of the flash through the video data.... but a micro gives me the flexibility to load the video data/memory by serial, SD card or other methods.

Regards Joe

Thanks I have been reading the book Video Demystified by Keith Jack

720 samples of video that are composed of Y and Cb /Cr 720x2 = 1440 byte samples per line.

I can probabaly wite code in the micro to fill in the synch and frame data from lines 1 to 22 and 311 to 335 and 624 to 625

Regards Joe