Could you explain this in a little more detail?  I'm not understanding why HDMI would influence jitter of the downstream system.  HDMI is a packet-based digital protocol, how does the rate at which packets arrive influence the analog performance of the device?

Unless the DAC is actually clocked off of the HDMI clock (which would be tough since a lot of different HDMI clocks are possible), the DAC's jitter shouldn't depend on if you fed it with HDMI or any other input.  Just like how playing Spotify vs. iTunes doesn't change the jitter in your sound card.

Quote from: saratoga on 2015-09-02 22:45:09

Could you explain this in a little more detail?  I'm not understanding why HDMI would influence jitter of the downstream system.  HDMI is a packet-based digital protocol, how does the rate at which packets arrive influence the analog performance of the device?

The rate at which the packets arrive is not the only relevant variable.

For example SP/DIF packets arrive in a fairly continuous stream while HDMI packets generally arrive with big time delays between them.

Audio is a fairly small percentage of a HDMI stream and the packets are relatively sparse.

Quote

Unless the DAC is actually clocked off of the HDMI clock (which would be tough since a lot of different HDMI clocks are possible), the DAC's jitter shouldn't depend on if you fed it with HDMI or any other input.  Just like how playing Spotify vs. iTunes doesn't change the jitter in your sound card.

You're right - the jitter that was observed with some AVRs and HDMI inputs should not have happened.  It is probably a classic case of the squeaky gear.  I seem to recall comparing Miller's jitter numbers to  the standards in:

Eric Benjamin and Benjamin Gannon, "Theoretical
and Audible Effects of Jitter on Digital Audio
Quality", AES Preprint 4826, presented at the AES
105th Convention, San Francisco, September 1998.

and Miller's data was too incomplete for a comparison.

I'm under the impression that by the time your audio card sees the audio data stream from these services, it has been cleaned up quite a bit.

Most DAC chips are fairly susceptible to jitter all by themselves, but the buffering that drives them (such as in CD players) has generally been pretty good.

Yeah something more is happening. You have to get HDMI data to a DAC at a rate that matches the DAC's clock on average.  There are two different ways you could do that, use your own clock which you speed up and slow down slightly so that its average sampling rate matches the HDMI's packet rate or run the DAC async from the rest of the receiver off of a clock you derive from the HDMI.  If you do the former, the pitch wobbles some tiny, tiny amount at a small fraction of a Hz but you don't care about the HDMI clock.  I doubt this is done much, and the wobble is probably much too low frequency to be detected.  If you do the latter, the obvious way to do this would be to take the HDMI clock and feed it into a PLL which would generate the clock you wanted while stabilizing it, making the HDMI clock irrelevant as well. 

If this problem really only happened over HDMI (as opposed to merely having a broken DAC), I'd guess they did something crazy like try to divide down the ~160 MHz HDMI clock to 48k without a PLL.  That would certainly give you some jitter.  It would probably also give you a pitch error since I doubt the HDMI clock is always an integer multiple of 48,000 . . .

People seem to extrapolate the problems some devices have to the HDMI interface in general.

Are there any recorded samples that are readily available which can be used to demonstrate an audible problem with poorly designed devices?

I didn't want to imply they are audible.

Quote from: saratoga on 2015-09-06 18:32:23

Yeah something more is happening. You have to get HDMI data to a DAC at a rate that matches the DAC's clock on average.  There are two different ways you could do that, use your own clock which you speed up and slow down slightly so that its average sampling rate matches the HDMI's packet rate or run the DAC async from the rest of the receiver off of a clock you derive from the HDMI.  If you do the former, the pitch wobbles some tiny, tiny amount at a small fraction of a Hz but you don't care about the HDMI clock.  I doubt this is done much, and the wobble is probably much too low frequency to be detected.  If you do the latter, the obvious way to do this would be to take the HDMI clock and feed it into a PLL which would generate the clock you wanted while stabilizing it, making the HDMI clock irrelevant as well. 

If this problem really only happened over HDMI (as opposed to merely having a broken DAC), I'd guess they did something crazy like try to divide down the ~160 MHz HDMI clock to 48k without a PLL.  That would certainly give you some jitter.  It would probably also give you a pitch error since I doubt the HDMI clock is always an integer multiple of 48,000 . . .

The HDMI spec contains a chapter that describes the clock regeneration in a receiver. While an implementation may choose any method it sees fit, the overall process is pretty clear and straightforward. However, there are two modes, depending on whether the video and audio clocks are coherent or not.

Quote from: saratoga on 2015-09-06 18:32:23

Yeah something more is happening. You have to get HDMI data to a DAC at a rate that matches the DAC's clock on average.  There are two different ways you could do that, use your own clock which you speed up and slow down slightly so that its average sampling rate matches the HDMI's packet rate or run the DAC async from the rest of the receiver off of a clock you derive from the HDMI.  If you do the former, the pitch wobbles some tiny, tiny amount at a small fraction of a Hz but you don't care about the HDMI clock.  I doubt this is done much, and the wobble is probably much too low frequency to be detected.  If you do the latter, the obvious way to do this would be to take the HDMI clock and feed it into a PLL which would generate the clock you wanted while stabilizing it, making the HDMI clock irrelevant as well. 

If this problem really only happened over HDMI (as opposed to merely having a broken DAC), I'd guess they did something crazy like try to divide down the ~160 MHz HDMI clock to 48k without a PLL.  That would certainly give you some jitter.  It would probably also give you a pitch error since I doubt the HDMI clock is always an integer multiple of 48,000 . . .

The HDMI spec contains a chapter that describes the clock regeneration in a receiver. While an implementation may choose any method it sees fit, the overall process is pretty clear and straightforward. However, there are two modes, depending on whether the video and audio clocks are coherent or not. You can't meaningfully discuss the situation when you don't know which mode is active. Furthermore, the signal source has a lot of influence on the process because it determines the mode and supplies the division/multiplication factors to the receiving device. It makes it harder to determine the guilty party when the result turns out to be wanting.

There is no need for the resulting clock to be jittery. If both sender and receiver are working well, the resulting clock can be just fine. People seem to extrapolate the problems some devices have to the HDMI interface in general.

I hope I put this in the right forum. You've probably been asked this a million times, but I trawled the web (mostly searching "dan lavry" + "jitter", as I figured he was the "master") as well as his forum, and I couldn't really find my answer, so I asked on his forum (which gave this response: http://www.lavryengineering.com/lavry_foru...f=1&t=7449), and I'll also ask here to hear your opinion:

If we're talking home audio listening (not recording), is jitter then audible, and how does it sound? I'm only talking about playing CDs and digital audio files from either a CD player, or your computer or a streamer through a dac into your amplifier.
Let's also for the time being assume that the analogue to digital conversion during recording/mastering was done well to begin with, and let's assume that the converter you use is of fairly good quality.

I discussed this with an audiophile friend. My own impression is that with 16 bit audio, jitter starts to become audible at -96 dB (without dithering), so with music recorded at sensible levels, it will not be audible, as all jitter is in the noise floor, and the music would mask the jitter. An exception could of course be orchestral music with a huge dynamic range recorded at a very low volume (so the noise floor would be raised). As for how jitter sounds, the video "Digital show & tell" on Xiph.org says quantization noise sounds like tape hiss from analogue tapes, but I might be mixing up quantization noise with jitter (is it the same?). On that website, there's also a file available for download with a 1 kHz tone at -105 dB. When playing that file there's background noise, which I assumed was jitter. In other words, jitter is present in all digital audio, but the amount is so low that you can never hear it except for in those extreme cases mentioned above. I asked Ethan Winer who said:
"Jitter manifests as noise 100+ dB below the music, and is never audible. Nor does it create 'a lack of depth, solidity and a smearing of the stereo image.' You’re thinking of wow and flutter. :->)"

In Ethan Winer's Youtube video "AES Damn lies workshop", he shows the following picture:



My friend's attitude is that jitter is omnipresent and always audible and smears the stereo image etc. (like the comment above), so although he exclusively listens to digital audio he is starting to think vinyl might be the way to go to get rid of the issue of jitter. Surface noise, pops, clicks, etc. from vinyl can be filtered out by our brains, whereas jitter is an omnipresent 'grating' and unpleasant sound.

I of course understand that when creating converters like Dan Lavry does, it's important to minimise jitter as much as possible in order to come closer to creating the perfect product, as well as creating an A/D converter that will have minimal jitter so the recording artists can raise and lower levels on different tracks as much as they like. But as mentioned, I'm only interested in audibility and listening at home – not in the technical aspect (measuring, etc.).

Marantz claims to have Jitter reducing technology. Now I don't think a company as large and as well regarded as Marantz would include a technology in their equipment that didn't have real value ... I trust that their engineers know exactly what they're doing and that reducing jitter matters. I don't think Marantz would spend money on a "non issue".

Marantz claims to have Jitter reducing technology. Now I don't think a company as large and as well regarded as Marantz would include a technology in their equipment that didn't have real value ... I trust that their engineers know exactly what they're doing and that reducing jitter matters. I don't think Marantz would spend money on a "non issue".

I trust that their engineers know exactly what they're doing and that reducing jitter matters. I don't think Marantz would spend money on a "non issue".

Or....you don't really understand how companies sell products to consumers do you?

Even depending of the technology the effects can vary, as in CD player with a clock signal to the DAC with 1us jitter can have a disastrous effects if it uses a 1bit DAC but at the same time be unnoticeable if it uses a R2R DAC.

The only time that I was able to hear jitter noise in a CD player was in an +20 years old one from a friend (actually his father), I reworked it and the noise and jitter disappeared (caps where bad, some diodes and transistors where also bad an changed the crystal oscillator module as it drifted to much).

No expert here, but if someone wants to describe how jitter sounds, wouldn't it be very similar to a Doppler Effect. But It would be a Doppler Effect that changes many times per second in very small acceleration changes.

I don't know much about jitter in audio, but I do know about jitter in networking. So I'm extrapolating the concept. In other words, it's my guess.

For Analog sources, jitter would be due to the change of speed of the media during playback. Not so much the overall speed, but tiny acceleration or declaration of the playback speed. Or instability of the playback speed. I would expect this to be inevitable but at the same time mostly negligible. It's part of the nature of electric motors and belt drives, etc.

For digital sources then you have the instability of the clock. Which will depend on the quality of the oscillator. But then again when you have 44,100 samples per second, can you tell which of those samples came a little faster or slower?

The only way you could probably hear jitter on a real world scenario would be an Analog system which is pretty much failing dew to mechanical flaws. It could be experiencing excessive mechanical resistance. It could be worn out, Or it could be affected by a power problem like low voltage. So you could probably listen it it slow down for longer periods of time and then go back to normal.

On a computer you could probably listen to some sort of jitter if the computer hangs momentarily. Then you might listen to the audio slow down or pause, and then try to catch up. If there is a slow down or catch up it would be jitter. If it just skips during the problem, then you wouldn't actually be able to hear the jitter it would just be a skip.

"Headbanging jitter.... Someone had jokingly mentioned that jitter that comes from the doppler effect, if you move your head, is probably higher than jitter introduced by the devices themselves."

[A] CD player with a clock signal to the DAC with 1us jitter can have a disastrous effects