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Question about VALID and HOLD in ADV212

Question asked by mamzq3 on Nov 11, 2010
Latest reply on Nov 17, 2010 by DaveD



I'm just beginning on a video project involving streaming video over an ethernet network, and have been looking throughly through the ADV212 user manual/datasheet/programming guide and have a few questions.


In my project, I think it's certain that there will be large periods of time (roughly ms in length? I'm not sure the delay yet, but as the max size of an ethernet packet is 1500 bytes, I would imagine I cannot send an entire frame in one packet) where I will have to stop reading the compressed data from the ADV212.


I understand that when in encode mode, I can assert the hold signal (to whatever set polarity to indicate a "HOLD" condition) to tell the ADV212 that I'm not ready to read more information. So, my question is (Question 1), how long can I hold the "HOLD" signal before the data becomes invalid, or will the data ever become invalid?


In my project I am decoding a NTSC composite signal (using the ADV7180), feeding the required lines to the ADV212, and then will have some controller between the outputs of the ADV212 and an ethernet controller.


(Question 2)

I'm unfamiliar with the JPEG2000 compression algorithm, but from scanning a few of the other threads, this is how I imagine the chip works (in JDATA mode, encoding mode):


1. The ADV212 takes in uncompressed data (over the VDATA bus) until a full image is formed inside the ADV212.

2. The ADV212 will perform the algorithms used in JPEG2000 compression methods.

3. When the ADV212 is finished performing the compressing, the VALID signal is asserted, and when the HOLD signal is de-asserted, data can be sampled from the JDATA bus. When the HOLD signal is asserted, the data waiting to be output (inside the ADV212... not on the JDATA bus) will continue to be valid and will be output when the HOLD signal is de-asserted.

This continues until the last compressed byte in the ADV212 is output on the JDATA bus, right?


(Question 3)

As far as the ADV7180 goes, how do I go about feeding the VS and FIELD signals (both use pin 37 in the 40 pin package) to the ADV212?


I sincerely appreciate any help, or any suggestions!!