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Jitter and Packets and Encryption

post #1 of 3
Thread Starter 
I have read that packet based transmission such as DD/DTS is not subject to jitter. I have also read that it is subject to jitter.

Meridian has an encryption process called MHR (Meridian High Resolution) which some users claim reduces jitter, possibly by randomizing it during encryption and de-encryption. Yet no one claims that HDMI has lower jitter because of HDCP. Plus when DD is sent via HDMI, HDCP is usually applied, which would make it both encrypted and packet based, possibly making it very low in jitter.

Have there been any studies regarding jitter and encryption and/or being packet based?
post #2 of 3
Jitter is a total non-issue, and it's not worth paying even 50 cents more for a device that claims "low jitter" as a feature. Jitter manifests as noise, and it would have to be 1,000 times worse than usual to be audible.

--Ethan
post #3 of 3
Hi GGA,
Quote:
Originally Posted by GGA View Post

I have read that packet based transmission such as DD/DTS is not subject to jitter. I have also read that it is subject to jitter.
Both are correct and both are wrong.

The transmission of packets is basically asynchronous with the playback, and therefore has no inherent jitter. However, the "player" (typically an AVR) needs to time the playback with the rate that the packets are arriving, to prevent overflow/underflow of its packet buffer. That is not a trivial process, and the synchronizing of playback to packet-timing can and does introduce jitter. How much jitter is dependent solely be the playback device itself, as determined by the engineering effort that went into controlling the jitter.

So, yes, there is jitter. No, the jitter is not in the packets. The jitter is caused by the fact that packets arrive at a rate determined by the source, and may or may not be handled well by the player.
Quote:
Meridian has an encryption process called MHR (Meridian High Resolution) which some users claim reduces jitter, possibly by randomizing it during encryption and de-encryption.
Encryption and jitter have absolutely no relationship. Again, the playback device is solely responsible for any jitter in the signal chain. There is no jitter during the encryption/decryption stage, and the audio has been decoded fully to PCM by the time it gets to the DAC (which is the only place where jitter is an issue).


Edit: Ethan posted while I was composing.

Ethan's point is important: Jitter is a measurable thing and so is the noise it generates. But even the worst jitter generates noise levels too low to be audible.
Edited by MarkHotchkiss - 6/17/13 at 12:39pm
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