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Discussion Starter · #1 ·
I have been thinking about the problem of recording HD content from DirecTV and had an idea / question...


Why not simply record the HD output from the STB (component, DVI, etc) by re-encoding to MPEG2? Or even better MPEG4?


It seems to me something that could encode the output from a PC video card (VGA, XGA, etc...) would also work for the HD signal?


If you convery to an OTA signal then it can be pumped into a PC card like the HiPix. It may be possible to loop it back though the OTA input on the STB where it could be send to a DVHS deck using a 169Time mod or a TS165?


I have looked around at the MPEG chip vendors and most support NTSC or PAL input but not HD resolution.


Does anyone know of anyone workign on this type of implementation?

Any obvious problems I am not aware of (macrovision type protection on the signal?)


John G
 

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Quote:
Originally posted by JG-AVS
Why not simply record the HD output from the STB (component, DVI, etc) by re-encoding to MPEG2? Or even better MPEG4?
It's not all that simple. You'd need an encoder that is 5-6 more powerful than the ones in any home deck (e.g. JVC DVHS, or Panny E30).


It would require something that will take 180MB/sec (DVI) or a DAC that would generate it (from analogue) and then the encode to a size that is provides acceptable quality, is real-time obtained, and small enough to be reasonably managed.


This is ignoring the fact that the MPAA would haul anyone creating such a device into court in a heartbeat.
 

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What you're asking about is a very difficult problem to solve. The bandwidth is high, and the amount of processing is therefore large. I have found no single chip that does the job.


dialog_gvf, it is *not* illegal to MPEG encode content that is already yours. Distributing said content afterwards, is another story. If I'm wrong, then we'd all better be hauled off to jail, what with using our Tivo's and VCRs all these years.


Dave.
 

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Discussion Starter · #4 ·
thanks for the feedback.


copen - How about using a bunch of MPEG chips in parallel?


For example: the 1080i signal is something like 1900 x 1080 pixels (right?)


You could feed each chip a manageable 640x480 chuck of the image:


Chip 1 – pixels 0,0 – 640,480

Chip 2 – pixels 641,0, - 1281, 480

Chip 3 – pixels 0,481 – 640, 961

etc…


Each chip would write it’s own 1 minutes files on the storage medium (kind of like the HiPix card ). This would obviously need to happen in real-time.


Something like:

Minute1_Chip1.MPEG

Minute1_Chip2.MPEG

Minute1_Chip3.MPEG

Minute1_Audio.MPEG

Etc…


A separate thread could merge all the files for a single minute into the full resolution MPEG file and delete the per chip files. This part would not need to happen in realtime.
 

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Record DirecTV HDTV to DVHS tape- Not a problem at all! Not for me or anyone else who just went and bought the proper equipment to do this.

You're new here. You are obviously not aware that there already is a comparatively low cost (compared to an MPEG2 HDTV encoder and audio mux for DD plus an MPEG2 VCR) device to record DirecTV. Plus you will also need a non-standard packet length to standard length translator for the non-standard MPEG2 data from DirecTV. For a whole lot less money I bought the only device available to the consumer, marketed to the consumer for recording DirecTV HDTV. It is not perfect but it does work and depending on your ability to operate the device properly will yield you satisfactory results. The company is still working on some parts of the process to perfect recordings on HBO but HDNet is perfect now as far as I am concerned. I am starting to collect quite a few HDNet programs here on DVHS HDTV from my Mits DVHS VCR. see- www.169Time.com or do some more reading in this section. The amount of time you spent trying to find a way around the Panama canal you could be doing what others already are.


Oh and BTW, I haven't received a letter from the MPAA yet. I really don't think they care.
 

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Quote:
Originally posted by copen


dialog_gvf, it is *not* illegal to MPEG encode content that is already yours. Distributing said content afterwards, is another story. If I'm wrong, then we'd all better be hauled off to jail, what with using our Tivo's and VCRs all these years.


Dave.
I'm not defending the MPAA or their continued fight against fair use. I'm merely saying that any manufacturer that tried to release an analogue HD recorder would be sued.


Probably by JVC too. With such a recorder you could copy DTheater tapes.
 

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Quote:
Originally posted by JG-AVS


copen - How about using a bunch of MPEG chips in parallel?
Interesting idea.


I'm not sure you can treat a single image as multiple images and get the same quality encoding.



If you really didn't care about real time, it might be possible to do the whole thing with a monster PC. Capture the DVI stream and store it temporarily on a hard drives (you'd need a 1.6 terabyte of storage for a 2.5 hour movie). Then, using an MPEG-2 encoder generate the encoded stream and output it firewire to a DVHS deck. That would probably take 10-20 hours.




If the ASICs for real-time HD encoding became cheap enough, a PC card could be the real-time encoder.



And another possibility is a cluster of PCs each working on a part of the HD encoding, with a master PC collecting and merging the results into a single HD encoded stream.
 

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"I'm merely saying that any manufacturer that tried to release an analogue HD recorder would be sued. "



So go out and buy a WVHS machine, (it is an analog HDTV VCR) connect it to your RGBHV outputs and record away. Then let us know how you are doing with your legal battle. My guess is no body will care. The product exists now, but is not digital. It is an analog recorder where the only copy issues would be Macrvision. Macrovision is easy enough to bypass and filter out. JVC who makes the WVHS, is not having any trouble selling them either. They are sold through the professional Presentation distributors in case you want to check them out. They are not cheap but far cheaper than the hack job you would do with the HDTV MPEG stuff.


Frankly I think some people just want to do this by a particular method. My approach is to get the archive tape on the shelf by what ever method and I have no problems using an existing product to do that. We are still talking about recording DirecTV HDTV aren't we?
 

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Quote:
So go out and buy a WVHS machine, (it is an analog HDTV VCR) connect it to your RGBHV outputs and record away. Then let us know how you are doing with your legal battle.
I don't think I ever recall reading or see anyone claiming that the powers that be would go after individuals using legally obtained equipment.


The MPAA isn't all powerful around the world, so I'm sure there is equipment available somewhere. But, it isn't consumer equipment, or it isn't here.


A WVHS (analogue) recorder is an option (e.g. JVC SR-W5U). They come out of the the old Japanese analogue HD days (1125 scan line). But, they are professional equipment and VERY expensive (MSRP for the SR-W5U is $5000)

Here's a link . Rent one for three days for the price of buying a JVC DVHS deck.


And, I have no idea what the quality would be like relative to simply recording the digital feed for later decoding.
 

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Quote:
copen - How about using a bunch of MPEG chips in

parallel?
All real-time HDTV MPEG-2 encoders use multiple chips

in parallel. I've attached a JPEG of the output from

an MPEG-2 bitstream analyzer. It's showing the quant

level of macroblocks from a difficult to code I-frame

of Bikini Destinations. Each chip is running out of

bits independently, and it's quite obvious that each

chip is handling 8 macroblock rows. Since there's

68 macroblock rows in a 1080i image, this encoder is

using 9 chips to encode 1920h x 1080i HDTV.


BTW, I couldn't capture the whole 1920h x 1080v image,

so it's cut off top, bottom and to the right.


Ron
 

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JG-AVS,


It's too much work to hook up and handhold 9 chips at once. Too expensive, too complex. There has to be another way.


BTW, W-VHS is a very good option. One went for $750 a few days ago on Ebay. I missed it by a couple of hours!


Dave.
 

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Technology does march on. The new generation of MPEG-2

encoder chips can do 1920h x 1080v in three chips.


On a historical note, the first MPEG-2 encoders delivered

to DirecTV in 1995 were 14 chip monsters. 8 chips for

NTSC (9 chips for PAL) to do the DCT and VLC coding, 4

chips for adaptive field/frame motion estimation, 1 chip

for inverse telecine and 1 chip for VITC timecode control.


Seven years later, we have single chip MPEG-2 encoders

inside of consumer electronics (DVD recorders and JVC

D-VHS).


Ron
 

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Quote:
Which chipset can do HD encode in 3 chips?
The C-Cube (now LSI Logic) Domino is capable of HD

encode in 3 chips. Here's a link to the device:

http://www.lsilogic.com/techlib/mark...no_arch_pb.pdf


Unfortunately, LSI does not currently provide any HD encode

software for Domino. That's up to customers to provide

(usually under some partnering arrangement so that they

can start with the baseline SD resolution code).


Ron
 

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There's a lot more to an HD encoder than three MPEG chips. First the analog video must be digitized. Remember that television is synchronized data. That means the write clock of the buffer RAM must be synchronous with the incomming video. PLL's at these rates (74.25mhz) are pure good old analog circuits with the all the electrical engineering know-how involved. And as you can see, at these clock rates, circuit layout path timing is critical. The stream must then be muxed into a format the encoder chips require. There will be a lot of glue logic in between. at these speeds, that's some expensive FPGA's and the complilers to build them.


Oh, and then there's the audio. That must be fornmat converted and muxed in.


This is not a DIY project.
 

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Quote:
This is not a DIY project.
Yes, but I think copen was doing some research for his

professional activities.


I agree that an analog input encoder would be a nightmare.

I don't know of any off the shelf HD component input A/D

converters. DVI input might not be that bad.


Another historical note. When I was at my previous company,

we looked at adding AC-3 audio encoding to our products.

At that time (1998), the reference 5.1 channel AC-3

encoder from Dolby used three high performance Motorola

DSP processors running in parallel.


Ron
 

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Discussion Starter · #19 ·
Thanks to everyone for the feedback. As mentioned this is not a DIY project so hopefully some corporation will make a move in this direction when the underlying technology becomes more mature.


In the long run, I think this is the way the technology will be headed. As HD-DVD emerges it will only be a matter of time before HD-DVD RW drives will become available for the home computer. I for one would rather have a stack of HD-DVD Rs as opposed to tapes.


John G
 
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