HDMI to VGA converter that supports 1080i50 from your experience - Page 1
Forum section: electronics / general

author: Axk
author_rank: Regular Contributor
timestamp: August 14, 2018, 12:32:34 pm
content: Got a TV receiver that outputs 1080i50 and want to connect it to an old (2005-2006) Samsung 17" LCD.Got a cheap $4 converter from ebay but it doesn't work for this scenario (doesn't work for 1080p50 either and even with a new full HD LCD)Ebay has other HDMI -> VGA converter that explicitly specify 1080i50 support.So I wonder if these will work, if anyone has experience with these in simular circumstances.Or maybe because the 17" monitor doesn't support 1920x1080 I'm out of luck with any converter?Particularly interested in the Seed Studio converter (because I can buy it locally without having to wait for a month or 2 for an ebay order).

author: senso
author_rank: Frequent Contributor
timestamp: August 14, 2018, 01:21:34 pm
content: If the monitor doesn't support 1080p res no converter will do magic..

author: Axk
author_rank: Regular Contributor
timestamp: August 14, 2018, 01:34:59 pm
content: Of course it won't display 1080p, but I thought maybe the converter could resize the picture, why not, at least theoretically.

author: bob225
author_rank: Frequent Contributor
timestamp: August 14, 2018, 03:38:03 pm
content: The cheap adapters are nothing more than a pin changer - you either need a tv/monitor that does 1080 or change the settings of tv receiver output (if possible)

author: wraper
author_rank: Unknown
timestamp: August 14, 2018, 03:51:51 pm
content: Quote from: bob225 on August 14, 2018, 03:38:03 pmTrue only for DVI-I to VGA converters, HDMI does not have necessary pins to output analog via passive converter. Moreover in the past I bough active HDMI-VGA converter for around $2.

author: Axk
author_rank: Regular Contributor
timestamp: August 14, 2018, 04:24:12 pm
content: bob225, thanks for the tip, didn't think about changing the settings on the TV receiver, will see if it has this option.As to the cheap converter I have (it's not broken because it works from my tablet to the old LCD) it does have a chip inside which is some obscure name that I cannot find a datasheet for, but they sell the chip for $3 from China.

author: bob225
author_rank: Frequent Contributor
timestamp: August 14, 2018, 04:29:04 pm
content: My bad. I was thinking dvi of course vga is analogue and hdmi is digital so need to be activeYou could use a hdmi to vga scaler but the cost is as much as a cheap monitor

author: wraper
author_rank: Unknown
timestamp: August 14, 2018, 04:36:37 pm
content: Quote from: Axk on August 14, 2018, 12:32:34 pmOf course it does not. You should not expect anything over 1280x1024. It might support something higher but certainly not 1080pQuote from: Axk on August 14, 2018, 01:34:59 pmDumb active converter cannot do any resolution scaling. You would need much more complicated hardware to do this.

author: gnif
author_rank: Unknown
timestamp: August 15, 2018, 05:30:15 am
content: Just a word of warning, many of these devices pull too much current from the HDMI port, and will do odd things on certain video cards, or at higher resolutions. I have a few cheap $3 ebay things that I have hacked a molex connector into to provide the 5V from the PC's psu directly.

author: Axk
author_rank: Regular Contributor
timestamp: August 15, 2018, 10:48:24 am
content: gnif, this was my first thought on why it didn't work in my case.Conviniently they provisioned for a power micro USB connector on the PCB so it was easy to add that, but it didn't help.I also read that the small chip may overheat because of lack of heat sinking and this may cause issues and this happens in my case in the case when it actually works from a tablet to the LCD monitor.

author: macboy
author_rank: Super Contributor
timestamp: August 15, 2018, 06:10:57 pm
content: A cheap adapter will not alter the signal timing. HDMI/DVI are very much similar to VGA, having red, green, and blue signals (or YCC) plus a horizontal and a vertical sync signal. A cheap adapter is nothing more that a chip which receives the TDMS RGB signals and converts them to analog (possibly doing YCC->RGB conversion). The sync signals are passed through unaltered. This works fine when the signal is within the sync range of the analog (VGA) monitor you are using, and it fails otherwise. Horizontal resolution is essentially arbitrary for analog signals (resolution is simply related to bandwidth) but the vertical resolution is dictated by the ratio of the horizontal and vertical sync signals. I'd suspect that your monitor does not like the 50 Hz vertical refresh rate, or possibly doesn't like the vertical resolution or the size of the "porch" (blank) areas in the 1080p signal, as they are not quite the same as computers typically used.You could try a smart converter which will capture the HDMI input into a framebuffer then scale that and output it at a resolution and refresh rate that you can choose. These are much more complicated and more expensive than the cheap ones which are basically just a few DACs.

author: wraper
author_rank: Unknown
timestamp: August 15, 2018, 06:52:23 pm
content: Quote from: macboy on August 15, 2018, 06:10:57 pmNot really. For LCD it does matter. If horizontal timing is not right, it just won't sync. It still needs to recover original digital resolution from analog signal, so both vertical and horizontal timing is very important.

author: Axk
author_rank: Regular Contributor
timestamp: August 15, 2018, 07:09:49 pm
content: macboy, wraperWill hook up the VGA output to my oscilloscope to see if it produces any output on HSYNC and VSYNCThinking about a project of builing such a converter with an HDMI receiver, FPGA and VGA DAC, have found an Analog Devices HDMI receiver in a hand solderable package and datasheets available. Not sure how difficult it might be to pull this off. Will need DRAM also I suppose to implement scaling so will need to control DRAM.Have not done impedance controlled routing also, I suppose I will need that also. Lots of stuff...Will try with the DAC and HDMI receiver on separate bords first I suppose hooking up the DAC to my FPGA dev bord to see if I can get it going and trying to at least read stream info out of the HDMI receiver to start with.

author: wraper
author_rank: Unknown
timestamp: August 15, 2018, 07:14:58 pm
content: DIY scaler just for the sake of one off DYI scaler is a stupid idea. Especially to attach monitor which is worth $15-20 in the best case. It's much cheaper to buy off the shelf scaler or another monitor. Not to say it will take tons of wasted time.

author: wraper
author_rank: Unknown
timestamp: August 15, 2018, 07:25:12 pm
content: Making own scaler would be useful only for the sake of learning, but then you could spend time making something more practical.

author: Axk
author_rank: Regular Contributor
timestamp: August 15, 2018, 07:31:53 pm
content: Just for the sake of learning of course. A brand new HDMI monitor would be cheaper with my current BOM estimate.

author: macboy
author_rank: Super Contributor
timestamp: August 15, 2018, 09:05:00 pm
content: Something like this should help you:https://www.ebay.com/itm/MHL-HDMI-to-VGA-Scaler-converter-up-to-1900X1200-60HZ-supported-for-PS4-PS3/282055759927https://www.ebay.com/itm/HDMI-To-VGA-Video-Audio-Converter-HD-1080P-Signal-Booster-Auto-Scaler-OSD-Menu/253757390792

author: bob225
author_rank: Frequent Contributor
timestamp: August 16, 2018, 01:11:00 pm
content: does the tv receiver have any other outputs eg, scart ?

author: Axk
author_rank: Regular Contributor
timestamp: August 16, 2018, 08:18:36 pm
content: It has a SCART output with RGB, but RBG is only supported in interlanced mode so it won't work with the monitor.

author: Axk
author_rank: Regular Contributor
timestamp: September 02, 2018, 02:31:22 pm
content: One of these scalers that macboy recommended just arrived.Works fine.Inside it's an HDMI receiver (Sil9293CNUC) followed by a specialized video scaling/conversion chip (MDIN-241H) and an audo DAC (CS4344) with an unlabeled QFP48 micro to control it all.Wonder if this is a 2 or 4 layer board.Also wonder how much on-chip memory does the scaling chip need to do scaling and de-interlancing with no external RAM present on the board, should be at least a few megabytes suppose.