In Reply to: Is HDMI asychronous (do higher precision clocks help HDMI)? posted by Brucemck2 on December 9, 2010 at 08:17:18:
HDMI is an abortion of an interface that was crammed down our throats by Sony and Hollywood. Silicon Image was the party that made it all possible.
The idea by Sony was to have the audio and the video both on the same cable, to avoid confusing the schmucks who buy their Sony TV sets at Best Buy and can't figure out how to connect it. Hollywood demanded "content protection", and it was decided that HDCP as developed by Intel would suffice. Silicon Image was determined to develop the silicon chips so that they could cash in on the cash cow.
Of the many problems associated with HDMI, the audio quality is totally handicapped for lack of -- a pin! They designed the connector before they finished designing the system. They didn't have enough pins to also have a master audio clock.
So with HDMI, the audio clock is derived from the video clock. For high-def TV, the video clock runs at either 74.25 MHz or 74.25 * (1000/1001) [thank you NTSC!!!]. The audio clock runs at multiples of 48 kHz. Of course, these are not related. So the receiver has a PLL to regenerate an audio clock based on instructions from the transmitter (source) telling it what to do.
The result is the worst jitter of any system yet invented. It truly sucks.
Much later, they added a thing called Audio Rate Control in HDMI 1.3a. This puts a buffer and the master audio clock in the receiver. Then commands are sent upstream on the CEC line telling the player to speed up and slow down as necessary to keep the buffer full.
The only people to use this are Sony (HATS) and Pioneer (PQLS), but both use proprietary implementations that prevent use with other equipment.
And the fee for using this pile of steaming dog dung? $30,000 per year in licensing fees. It's a beautiful world, no?
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Follow Ups
- HDMI has the highest jitter of any interface - Charles Hansen 13:45:55 12/09/10 (22)
- RE: HDMI has the highest jitter of any interface - rick5757@gmail.com 09:09:38 06/07/13 (0)
- WAIT! I've heard that Dolby TrueHD & DTS HD Master Audio ... - Feanor 16:32:39 06/09/11 (0)
- RE: HDMI has the highest jitter of any interface - JohanV 07:05:52 06/09/11 (0)
- Doesn't PS Audio acclaim its PerfectWave transport's link via I2S HDMI? nt - Norm 08:45:00 12/11/10 (1)
- Not the same thing ... - EmailTim 16:14:11 12/11/10 (0)
- So, the key to HDMI sonics is the PLL in the receiver? - Brucemck2 15:54:29 12/09/10 (15)
- RE: So, the key to HDMI sonics is the PLL in the receiver? - Charles Hansen 21:47:29 12/09/10 (2)
- RE: So, the key to HDMI sonics is the PLL in the receiver? - barrows 22:50:28 12/09/10 (1)
- It's the multichannel I am after : RE: So, the key to HDMI sonics is the PLL in the receiver? - Brucemck2 03:49:15 12/10/10 (0)
- The key to using HDMI is to not use it. - Tony Lauck 18:31:55 12/09/10 (11)
- RE: The key to using HDMI is to not use it. - fmak 09:05:21 12/12/10 (5)
- I wish... - Charles Hansen 09:16:11 12/12/10 (4)
- How 'bout Denon? - edward 11:23:24 12/12/10 (3)
- ARC = Audio Rate Control - Charles Hansen 14:20:39 12/13/10 (2)
- RE: ARC = Audio Rate Control - edward 22:44:25 12/13/10 (1)
- HDMI Overview - Charles Hansen 19:28:54 12/14/10 (0)
- Because it's the only way I can access latest lossless BluRay - Brucemck2 18:55:40 12/09/10 (4)
- RE: Because it's the only way I can access latest lossless BluRay - rmilewsk 13:51:34 06/09/11 (0)
- RE: Because it's the only way I can access latest lossless BluRay - nl1 07:53:47 12/16/10 (0)
- RE: Because it's the only way I can access latest lossless BluRay - cfraser 21:01:09 12/09/10 (1)
- RE: Because it's the only way I can access latest lossless BluRay - Brucemck2 03:43:58 12/10/10 (0)
- RE: Because it's the only way I can access latest lossless BluRay - Tony Lauck 19:09:09 12/09/10 (0)