Originally Posted by Glimmie
1) DVD and BluRay are not 44.1khz but ar 48khz. This is due to the required clock lock to video rates.
So we are down to nitpicking I see
. In that case, I will turn the tables and tell you that sample rates up to 96 Khz are required in Blu-ray players. It all depends on what the content is encoded at. I simply picked one example.
The clock phase is not going to jump based on different video data combinations. The 48K clock is divided down from the pixel clock - it has to be as the data is synchronous to it.
Yup and it will suffer from jitter just the same. The synchronous nature only applies to ability to extract the data, but not its absolute timing. Here is a good link to read more: http://www.tnt-audio.com/clinica/jitter1_e.html
. It is an old article but explains nicely in clear language how you can wind up with jitter even when you drive the clock as you state and use a PLL as you explain below.
2) The "control processor" I am talking about is the internal computer that controls the device. Like sliding the disk carriage in and out. These do run in the KHZ range. Sure their master clock may be tens of mhz but the actual SPI and Ic2 control busses run in the KHZ range.
You are way behind the times my friend
. The type of processors used in BD players are far more powerful. Gone are the days of the little micro lighting up the front panel on a CD player and controlling the drive. Indeed, there are a number of processors in a Blu-ray decoder, all running at hundreds of MHz. Here is an example processor from Sigma Designs which powers a number of Blu-ray players: http://www.sigmadesigns.com/public/P...SMP8640_br.pdf
* 333 Mhz Audio DSPs (3 of them!)
* 667 Mhz MIPS
* 333 Mhz MIPS CPU
Here is the Broadcom part used in Samsung and some other BD players:http://www.broadcom.com/collateral/pb/7440-PB02-R.pdf
They don't give you the CPU speed directly but you can deduce it is not in Khz range by:
* Dual 333/400-MHz 32-bit DDR2 interface
You are not going to find any low-end micro like you are envisioning. BD-J requires a ton of horsepower as do decoding of all the advanced audio formats in multi-channel. Even the front-end runs in MHz region given the fact that the Blu-ray drive spins at > 48 Mbit/sec.
SDi and HDSDI both can carry emebdded AES audio. As SDI and HDSDI are single wire transport protocols, the data is inhierently jittery. The clock is extracted from the data stream and relies on the scrambling of the bits to minimize excessive blocks of ones or zeros. Based on your logic that jitter in the stream affects the audio qualiy, then how does emebedded audio in SDI work?
You mean when they don't use house clock to sync everything together? If so, then yes, they also suffer from jitter if they attempt to convert the samples to audio as opposed to moving them from device A to device B. Keep in mind that we do not have house sync in consumer players.
I'll tell you how as I design broadcast systems and products for a living.
Ah, time to recite our resumes, eh?
So here is a bit of mine. I used to be VP engineering at two broadcast video companies (Abekas and Pinnacle Systems). While I didn't do hands on design there, I am very familiar with the space and standards used. Two of the products I managed won technical Emmy awards. So you could say we share a common experience in that front.
The reclocking arrests the jitter. As long as you can recover the data crossings, you can recover the data with full accuracy.
Again, we are talking past each other. We are not talking about whether you can recover samples correctly. We are talking about whether the timing of the output clock is impacted or not. Read the above article and see the example where RF noise on a S/PDIF cable causes jitter!
This has been done for years with SDI. Yes we worry a lot about jitter but not as it upsets subjective picture and sound quality. Because it doesn't. Excessive transport stream jitter means complete data loss plain and simple.
We are not talking about excess jitter. Nor are we talking about jitter in a communication channel. We are talking about audio samples not being converted to analog at precise time that were captured. If you ever so slightly change their positions, you make the system non-linear and create harmonic distortion. Perfect clock does not exist in real world. No PLL cleans up all jitter. But you can take steps to reduce jitter.
I think you have read too many stereo magazine articals about jitter in CD players. Most of those articals are wrong from an electrical engineering perspective and furthermore DVD and Bluray don't have those issues due to the strict timing requirments of the video processing chain.
Please, ask me who I am before you make assumptions about me
. I am an electrical engineer and have been in audio, video, computer, network, etc. field for 40+ years. I have also been lucky to have had jobs which allowed me to have the best toys in the world to play with such things and gain real world experience in addition to my own engineering know-how. In my last job at Microsoft, I helped drive the specs for HD optical formats and technology from my group ships in every Blu-ray player. So I don't just read a magazine and come and post here.
The bottom line is that there is a completely different science and approach to high-end audio and video. Anyone can build something that puts out audio and video. But it takes a lot more knowledge to know if they are both right. Joe Kane would be out of a job if people knew even simple concepts of what color space to use. You wouldn't believe what we went through with Toshiba to make sure their HD DVD players programmed the HDMI transceivers to not do conversion to faulty 4:4:4, blow levels, not produce proper 24p, etc. Yup the device put out an image that impressed many but it still wasn't right until later firmware fixes.
And there is absolutely nothing in Blu-ray spec that makes the format perform any better than DVD. It reads the data like one did from DVD and sends it out. So I don't know what you mean by strict timing requirements.
Anyway, I hope you keep an open mind as you read all of this. The whole world of high-end audio/video is not made up of lunatics who hallucinate these things. There is science involved. And people who know what they are doing.