| View previous topic :: View next topic |
| Author |
Message |
cabrio_leo
Joined: 16 Apr 2008
Posts: 2
Location: Germany
|
 Link Posted: Wed Apr 16, 2008 7:13 pm Post subject: |
 |
|
Hi all,
the first batch got an filter added additionally to improve some edge enhancement issues. Are WTS and drudozucker writing about a second filter in addition to this one? I am a little bit confused which one they mean.
Bye
Leo
|
|
| Back to top |
|
 |
kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 17860
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
|
|
| Back to top |
|
|
drudozucker
Joined: 04 Jan 2008
Posts: 38
Location: Portugal
|
| Link Posted: Thu Apr 17, 2008 11:49 am Post subject: |
|
|
| cabrio_leo wrote: | Hi all,
the first batch got an filter added additionally to improve some edge enhancement issues. Are WTS and drudozucker writing about a second filter in addition to this one? I am a little bit confused which one they mean.
Bye
Leo |
Hi Leo, if you look at the output traces I have recorded you can see that there is a ripple on top of the signal. This is either caused by insufficient output filtering (then curable with an additional filter which isn't available yet) or by problems in the design (then not easily curable by a simple filter). As it stands the EXT-HD provides a signal which isn't clean resulting in picture imperfections (this imprecision is not edge enhancement related but will affect the complete picture).
Just for completion the EXT-HD is in its present form unsuitable for 720p or 1080p at 50Hz because it uses the 60Hz timing for R,G,B. This results in a picture which is pushed to the left and squeezed horizontally, unfortunately more than most projectors will accept (and hence can correct).
I have informed Moome of these issues. Now I am waiting for a solution.
Hope this helps
Udo
|
|
| Back to top |
|
|
cabrio_leo
Joined: 16 Apr 2008
Posts: 2
Location: Germany
|
| Link Posted: Thu Apr 17, 2008 8:22 pm Post subject: |
|
|
Hi Udo,
I saw your output traces and the ripple on the signal. You wrote you have an ext-hd from the last (second) batch. In this case the filter must have been already installed in your unit normally. The units of the first batch got an filter added after the dac. Could you look into you unit whether the filter is installed or not? You can have a look in the attached file. It's moomes upgrade document.
I hope moome will got a fix for it! Any response from him? Which email address did you use? I mailed him several times but I have always used his address directly in Taiwan not his forum address here.
And as an European user too I hope that he will correct the incorrect timing at 50 Hz. I discovered the problems too you wrote about.
Leo
| Description: |
|
Download |
| Filename: |
EXT-HD_batch1_fixes.pdf |
| Filesize: |
785.07 KB |
| Downloaded: |
570 Time(s) |
|
|
| Back to top |
|
|
drudozucker
Joined: 04 Jan 2008
Posts: 38
Location: Portugal
|
| Link Posted: Fri Apr 18, 2008 9:18 am Post subject: |
|
|
| cabrio_leo wrote: | Hi Udo,
I saw your output traces and the ripple on the signal. You wrote you have an ext-hd from the last (second) batch. In this case the filter must have been already installed in your unit normally. The units of the first batch got an filter added after the dac. Could you look into you unit whether the filter is installed or not? You can have a look in the attached file. It's moomes upgrade document.
I hope moome will got a fix for it! Any response from him? Which email address did you use? I mailed him several times but I have always used his address directly in Taiwan not his forum address here.
And as an European user too I hope that he will correct the incorrect timing at 50 Hz. I discovered the problems too you wrote about.
Leo |
Hi Leo, Moome has received my details (some of which I reported here) and has responded that he will try to find a solution.
I suspect in order to prevent visible ringing the output filter is of too simple nature or maybe cuts-in at too high frequencies. It's an old problem that many purists believe that filtering of any nature would affect fidelity. Unfortunately they don't appreciate the inherit problem of digitized sources and the physics of converting digital back to analog.
BTW I only mentioned that I used an EXT-HD of the second batch because otherwise somebody would have asked me 
Regards
Udo
|
|
| Back to top |
|
|
WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
|
| Link Posted: Fri Apr 18, 2008 4:07 pm Post subject: |
|
|
I hope people don't expect Moome to do a mass fix on these units just because of this.
When you start talking about 5th order video filters like the Tag unit uses, you are talking more money to implement such a filter (and board space)and it's not something that can be retro fitted onto to a circuit board. Yes there is some very hi frequency ripple on the signal, will putting a 5th order filter on it improve it, possibly - maybe.
The problem is not Moomes it's the Manufacturers of the HDMI chip, in their data sheet all they recommend is a simply filter for any anti aliasing or sideband/clock suppression and they say no other filtering is required. Sometimes when you design electronics you take the manufacturer for what they say in the datasheets.
_________________
Thanks
Walter
|
|
| Back to top |
|
|
drudozucker
Joined: 04 Jan 2008
Posts: 38
Location: Portugal
|
| Link Posted: Fri Apr 18, 2008 9:45 pm Post subject: |
|
|
| WTS wrote: | I hope people don't expect Moome to do a mass fix on these units just because of this.
When you start talking about 5th order video filters like the Tag unit uses, you are talking more money to implement such a filter (and board space)and it's not something that can be retro fitted onto to a circuit board. Yes there is some very hi frequency ripple on the signal, will putting a 5th order filter on it improve it, possibly - maybe.
The problem is not Moomes it's the Manufacturers of the HDMI chip, in their data sheet all they recommend is a simply filter for any anti aliasing or sideband/clock suppression and they say no other filtering is required. Sometimes when you design electronics you take the manufacturer for what they say in the data sheets. |
Hi Walter, I like to disagree with your statement and this is why:
a) a suitable filter consists of just 2 resistors, 5 capacitors and 2 inductances (per channel). This costs next to nothing and requires (in SMD) very little pcb space.
b) I also disagree that a manufacturer of electronics could simply rely on a data sheet when designing a product. Data sheets of advanced electronics are prone to mistakes but more importantly it will always be necessary to test the performance of any new circuit against many parameters, one of which has to be S/N (signal to noise).
Out of own experience I have deep sympathy for small scale electronics manufacturers, their pressure and also their limitations, but nevertheless I think it is necessary to conclude that the EXT-HD has not been evaluated sufficiently before going into production - and this is the second batch. I suggest (if not already in place) that in-house testing at the manufacturer is supported with a small team of beta testers. That way instability (the control software is buggy), incompatibility (the product is not suitable for (all) 50Hz applications) and imperfection (noise, spurious outputs) can be more likely prevented.
I repeat that I am a big fan of the EXT-HD and the work Moome provides and more importantly there is definitely no need to point the finger at anybody, but that shouldn't mean we describe technical facts as what they are.
Regards
Udo
|
|
| Back to top |
|
|
WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
|
| Link Posted: Fri Apr 18, 2008 10:10 pm Post subject: |
|
|
Do you think he should be modding all these units to correct this minor flaw?
I also agree that a suitable filter could consist of a hand full of parts, but it's all the (R&D) designing / prototyping / testing etc changing/modifying etc which costs money/time which would get passed on to the customer.
Should he be doing more, yes I do think he should be doing more in the testing phase because there have been many bugs with a few of his products. Do I think you should get Tag quality at Moome pricing, no. And yes he is basically a one man operation and I don't know what he has for test equipment.
Bottom line, I think the product he puts out, barring the software bugs is damn good for the price.
_________________
Thanks
Walter
|
|
| Back to top |
|
|
drudozucker
Joined: 04 Jan 2008
Posts: 38
Location: Portugal
|
| Link Posted: Fri Apr 18, 2008 10:43 pm Post subject: |
|
|
| WTS wrote: | Do you think he should be modding all these units to correct this minor flaw?
I also agree that a suitable filter could consist of a hand full of parts, but it's all the (R&D) designing / prototyping / testing etc changing/modifying etc which costs money/time which would get passed on to the customer.
Should he be doing more, yes I do think he should be doing more in the testing phase because there have been many bugs with a few of his products. Do I think you should get Tag quality at Moome pricing, no. And yes he is basically a one man operation and I don't know what he has for test equipment.
Bottom line, I think the product he puts out, barring the software bugs is damn good for the price. |
Hi, I don't think there is a need for correction of products already sold, because the deficiency can be considered minor in the context of the price. That's what a judge would say, trust me. However, I definitely will try to get rid of the spurious output because otherwise I don't believe that I would do justice to the ability of HD. The same should be the case, so I think, for future customers.
There is very little necessary to test the S/N at the level remaining within the EXT-HD, an 250MHz oscilloscope will do. There is also very little necessary to design the filter. Having said this, I fully appreciate the limitations of a small firm (I said this before  ), hence my suggestion of beta testers. This expands the scope without adding cost.
As a personal note: if you are a small operation you might better concentrate on things essential, hence I (but that is me!) wouldn't have added a Component input or Gamma correction circuitry. I would simply have focused on the demand of how to send 1080p to a display device without HDMI input.
Quality is unfortunately not strictly linked to price as many, many examples of high-end audio and video equipment has shown. There are excellent products at reasonable cost and poor products at astronomic prices - just think of some audio cables 
Finally, I like to say, that I was merely responding to this thread (I didn't start it) because there were comments which could in my opinion be interpreted as if there would be no need for improvement or if improvement would be difficult or expensive to achieve. That simply isn't the case and that's all I wanted to say. Having been closely involved with high-end electronics for all my life, I have offered my assistance to Moome (well before I even responded to that discussion).
So please read my comment as what is is intended to be: a technical discussion and not a fight for being right or wrong or pointing the finger at anybody.
Regards
Udo
|
|
| Back to top |
|
|
WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
|
| Link Posted: Fri Apr 18, 2008 11:03 pm Post subject: |
|
|
Unfortunately I don't think the HDMI all in one IC that is in the current ext HD unit is at the high end of the scale for HDMI/RGB devices. Let me know if you happen come up with a simple filter which cleans up the output.
His upcoming units will be using a separate HDMI and video dac setup. And for this one I've talked to the video dac apps eng from the manufacturer of the dac and he assured me that no post filtering for anti aliasing/sideband suppression is required on this dac for any HD video except for maybe a ferrite bead to suppress any hi freq noise but he said it wasn't even needed as the noise was way down the scale.
_________________
Thanks
Walter
|
|
| Back to top |
|
|
drudozucker
Joined: 04 Jan 2008
Posts: 38
Location: Portugal
|
| Link Posted: Sat Apr 19, 2008 9:36 am Post subject: |
|
|
| WTS wrote: | Unfortunately I don't think the HDMI all in one IC that is in the current ext HD unit is at the high end of the scale for HDMI/RGB devices. Let me know if you happen come up with a simple filter which cleans up the output.
His upcoming units will be using a separate HDMI and video dac setup. And for this one I've talked to the video dac apps eng from the manufacturer of the dac and he assured me that no post filtering for anti aliasing/sideband suppression is required on this dac for any HD video except for maybe a ferrite bead to suppress any hi freq noise but he said it wasn't even needed as the noise was way down the scale. |
Hi Walter, could you kindly let me know the product description of the all-in one HDMI device used in the EXT-HD. I am somewhat surprised that you say (maybe I misunderstood) that the used device has already a video DAC onboard. I am surprised because the modification instruction for EXT-HDs of batch 1, the EXT-HD's product description and the restriction to analog 1080i for HDMI certified products seems to forbid this. Of course I can be wrong. The more I know about the EXT-HD the better can I be help. Please send a PM if you feel that such detail isn't suited for the forum.
I think that the performance of a "HDMI input to analog video output converter" will not be restricted by the HDMI device which should merely make the digital connection (incl. handshake) to the source. Performance will be mostly defined by a careful split of digital and analog circuitry (e.g. independent power supplies), use of ground planes to boost S/N, localized voltages stabilization, high quality DACs, well designed reconstruction filters and good video buffers.
Regards
Udo
|
|
| Back to top |
|
|
|
|
Forum FAQ
Search
Memberlist
Photo Albums
Register
Profile
Private Messages
Log in
