[Heuer]

Update on my search for SDI output on TiVo. Just had this message from PJ Hi-Fi in Guildford:

"Great news! The box has been looked at by the board manufacturers head programmer and they have written the custom software build required for the FPGA to work correctly with Tivo. The box is now on its way back to us where we will fit the board properly, soak test and return it to you.

Thanks for your patience, we got there in the end

Best Regards

Elliot

Elliot Hicks

Custom Install Manager
Company Director

PJ HI-FI Limited
Tel / Fax: 01483 504801
[email protected] "

Just shows about anything is possible with TiVo and I commissioned this to prove it. Not had the box back yet but I will add an update on video quality when I do.

 

[CarlWalters]

I'm curious why are you adding an SDI output to TiVo? I'm assuming you're tapping off (8 bit I presume) straight after the MPEG-2 decoder before the digits hit any analogue back-end - and then bolting on an SDI I/F? If you're using an FPGA to do this (and I know it can be done) then that could give you a nice useful programmable back-end to TiVo. What FPGA is being used? Are they giving you programmable access (JTAG or otherwise) to it? I'm excited about this (in a sad h/w way )

 

[Heuer]

No idea on the technical background, suggest you contact Elliot for more information. I decided to do it to see what could be acheived by by-passing the on-board DAC and letting my Lumagen HDP Pro scaler have more to work with. Getting rid of the flashing in Mode 0 being one goal, pushing the TiVo knowledge base being the other.

It does indeed open up a number of other opportunities and given this was a custom software development, at my request, there is a gateway for more enhancements.

 

[CarlWalters]

well - I'd be very interested to hear what you get up to with it. And am happy to lend my "ahem" expertise if there is now a hackable FPGA that you can get access to.

I suspect though that bypassing the DAC may mean that the MPEG artifacts are a little bit more visible - having not ben smeared by the analogue backend. I hope I'm wrong though.

 

[CarlWalters]

and just having a look at the convergant site they say that the advantage of having SDI in is

... that the video goes through less digital to analogue and analogue to digital conversions. This results in more detailed image with less artefacts. Below are some simplified flow diagrams:

More detailed - yes.
Less artefacts - hmmm - I'd say different artefacts.

 

[Heuer]

Time will tell as I have not had the unit back yet. More info from Elliot:

" The mod will be slightly above the standard cost due to the requirement of a special software build for the SDI board. Not to bad though at £350, only £25 more than our normal mods. As for performance, i need to see some decent material through it as we have not set anything up on this one, i'm sure once Heuer has finished with all his hacking bits it will be awesome. The OSD'd are razor sharp."

 

[CarlWalters]

Time will tell as I have not had the unit back yet. More info from Elliot:

" The mod will be slightly above the standard cost due to the requirement of a special software build for the SDI board. Not to bad though at £350, only £25 more than our normal mods. As for performance, i need to see some decent material through it as we have not set anything up on this one, i'm sure once Heuer has finished with all his hacking bits it will be awesome. The OSD'd are razor sharp."

£350 - Ouch! If you have access to a friendly Xilinx or Altera representative then they can usually be persuaded - if they want your company's business - to part with one of their nice little SDI capable development cards - usually with a multirate HD/SD SDI capable FPGA plus cable equalizers and drivers for free. It would need a small amount of tweaking to hook up the FPGA to the TiVo MPEG Decoder backend - but not a huge amount.

 

[Heuer]

Great idea although I do not have access to any of that kit. If you do then please pursue it and let's compare notes and increase the knowledge base.

 

[bardsm]

is that a £350 charge to convert your existing tivo

That is an awful lot of money to spend when you consider HDTV is not too far away and hardware to exploit it is sure to follow. I wonder what the quality of the modded tivo is like to a standard sky+ (not talking about functionality of course)

 

[Sneals2000]

is that a £350 charge to convert your existing tivo

That is an awful lot of money to spend when you consider HDTV is not too far away and hardware to exploit it is sure to follow. I wonder what the quality of the modded tivo is like to a standard sky+ (not talking about functionality of course)

Sky + is still likely to look better than an SDI output modded Tivo fed by a Sky box. Even with a Mode 0 hacked Tivo you are still adding an extra MPEG2 encode/decode process (done using low-end, low-cost MPEG2 encoding kit) which Sky + doesn't have.

The best bet would be an SDI modded Sky+ if you were after the best picture quality.

 

[Heuer]

The best bet would be an SDI modded Sky+ if you were after the best picture quality.

SDI mods on all new (V2) Sky+ boxes is impossible as the MPEG decoder and DAC are on the same chip, so no way in. You can still mod the older SKy+ boxes but the cost is the same as for TiVo.

Modded TiVo will be here tomorrow so I can report on what the output looks like. I only did it to prove it was possible and for a bit of fun. Not suggesting others follow but it seems clear that Sky and others are determined to make their machines unhackable and unmoddable. - but no surprise there.

 

[Heuer]

SDI TiVo is now installed and working. Performance is excellent with no screen flashing on Mode 0. Picture quality is absolutely superb with more natural colours than using RGB/Component - both are connected so I can switch between them very easily. I would say it is impossible to tell the difference between Aux and SDI and I am viewing it on a very high grade 50" Pioneer Plasma screen and both fed via the Lumagen

So it can be done and I am personally delighted at the result - a large step forward.

Cost:

SDI mod: £350 (I also paid the one off TiVo software development cost)
SDI high grade cable: £40

Obviously a SDI enabled scaler is required but I already had the Lumagen HDP-Pro in my system anyway.

Edit: My wife, who normally has no interest in these things, just described the picture as "three dimensional".

 

[philask]

That is one SCARY picture.. don't think I'll be modding my Tivo like that anytime soon!

 

[Heuer]

Certainly not a DIY project!

 

[CarlWalters]

Certainly not a DIY project!

I have to say I disagree . I'd have said that that looks pretty do-able - if you're at ease with a fine-tip soldering iron and have worked on TQFPs or similar before. It would require a bit of patience - but could be done.

I have to say I'd be a little concerned at the mechanical stability of all those flying leads though. I can see they're encased in "gunk" but it wouldn't take a lot to knock one loose I reckon.

Still it's an interesting mod no doubt.

 

[Heuer]

Leads are well soldered and secured with silicone. It survived being sent from PJ Hi-Fi to the Software designers and back. Then it was sent via the TNT bruisers to me. Not planning on moving it around anymore!

 

[Sneals2000]

SDI TiVo is now installed and working. Performance is excellent with no screen flashing on Mode 0. Picture quality is absolutely superb with more natural colours than using RGB/Component - both are connected so I can switch between them very easily. I would say it is impossible to tell the difference between Aux and SDI and I am viewing it on a very high grade 50" Pioneer Plasma screen and both fed via the Lumagen

So it can be done and I am personally delighted at the result - a large step forward.

Cost:

SDI mod: £350 (I also paid the one off TiVo software development cost)
SDI high grade cable: £40

Obviously a SDI enabled scaler is required but I already had the Lumagen HDP-Pro in my system anyway.

Edit: My wife, who normally has no interest in these things, just described the picture as "three dimensional".

Interesting that you're not getting flashing in Mode 0. This must nail it down to being a D/A issue rather than an MPEG2 decoding one?

Interesting that you don't see much difference between AUX and SDI - though presumably an SDI modded Sky box (or Sky+ box) might show more of a difference as it will not have been D/A and A/Ded anywhere after the camera in the broadcast process? (Bit like watching Freeview via a DVB-T capture card in a PC)

 

[Heuer]

Interesting that you're not getting flashing in Mode 0. This must nail it down to being a D/A issue rather than an MPEG2 decoding one?

Interesting that you don't see much difference between AUX and SDI - though presumably an SDI modded Sky box (or Sky+ box) might show more of a difference as it will not have been D/A and A/Ded anywhere after the camera in the broadcast process? (Bit like watching Freeview via a DVB-T capture card in a PC)

So far not a single flash on a mixture of programmes suggesting the DAC chip was causing the problem rather than the IBM MPEG decoder. But I will remain vigilant

The picture is now so good I cannot think there is much room for improvement even with a SDI Sky STB, and any difference would be lost at a 6 ft viewing distance. There are no visible artifacts and pictures have lost that TiVo colour glow. I am sure the picture will improve still further as Lumagen release more software enhancements to their PAL de-interlacing algorithms.

Out of interest I made a MPEG/VOB copy of a programme (purely for research) onto DVD and compared that to the TiVo original. Played back through an Arcam DV27A SDI there was no difference in picture quality suggesting the TiVo MPEG decoder is a resonably competent chip.

 

[Sneals2000]

Yep - AIUI most MPEG2 decoders these days (and for the past few years) are pretty good performers. MPEG2 was designed to be assymmetric in its processing requirements AIUI - requiring far less number crunching for quality decoding than encoding. (The current caveat to MPEG2 decoders is that many have a "chroma bug" - due to a mistake in implementing the correct interlaced chroma sub-sampling structure for MPEG2 4:2:0 AIUI)

The more interesting comparison is between the MPEG2 encoding performed by the broadcaster on uplink for DSat/DTT and the MPEG2 encoding performed in the Tivo.

 

[Dibblah]

(The current caveat to MPEG2 decoders is that many have a "chroma bug" - due to a mistake in implementing the correct interlaced chroma sub-sampling structure for MPEG2 4:2:0 AIUI)

Which, unless I'm reading it wrong, does not rear it's ugly head unless you're talking about progressive output, which here in PAL land isn't too common still.

Link

Cheers,

Allan.