I am having problems getting the audio synthesizer in the ADV7441A working properly for HDMI 1080p59/60 video formats.
I am working on a mature H.264 encoder design that operates correctly for all other implemented video formats 1080p(24/23), 1080i(60/59/50), 720p(60/59/50), 576i(50),and 480i(59). We are now attempting to implement 1080p(60/59).
I am attempting to use HDMI 1080p59 video with a 48Khz audio sample frequency and a 256fs MCLKOUT master audio frequency output.
It appears that I am having problems with the audio synthesizer creating an accurate and stable output which results in audio/video synchronization issues on 50% of my prototype boards.
I have implemented the recommended audio synthesizer clock divider fix (writing 0x05 to HDMI map register 0x47 and resetting synthesizer).
I observe the following behavior one of my failing test boards:
The ADV7441A begins by correctly outputting my expected 12.288MHZ audio output clock.
(This is measured with a 1.3GHz frequency counter as aprox 12.288157 MHZ with my source and test unit).
As the ADV7441A heats up the frequency drifts slower (observed as low as aprox 12.28790 MHz on my test system).
Cooling the ADV7441A immediately returns the MCLKOUT to the expected 12.288157MHZ (Package temperature never exceeds 50degC).
The Video Clock output always remains stable and accurate at the expected 148MHz (aprox 148.35356 MHz on my test system).
This would indicate to me that although I have implemented the recommended audio synthesizer fix I am still having problems with the Audio PLL/synthesizer.
I believe that I have the Audio PLL loop filter set up as recommended ((1.5K in series with 80nF) in parallel with 8.2nF).
Any ideas or know issues?