nilsk123
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Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 1:30 pm

Hello,

I recently purchased a raspberry PI model b+. I have installed raspbian on a brand new microsd and booted the raspberry pi.

The raspberry pi boots succesfully! I know this because ive installed an rdp server via putty and can now remote desktop into it, its running like a charm. The problem however is composit video through the new 3.5mm jack. I have to cables from jack to tulip. One of which only shows black and white, and very blurry video. The other one just shows weird fragments.

I have tried everything regarding the config.txt. I am using an old PAL tv, so i set the sdtv_mode to 2, and aspect ratio to 4:3

my tvservice -s shows state 0x80002 [PAL 4:3], 720x576 @ 50.00Hz, interlaced

Does anyone know how this is possible?

Nils

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 2:01 pm

nilsk123 wrote:Hello,

I recently purchased a raspberry PI model b+. I have installed raspbian on a brand new microsd and booted the raspberry pi.

The raspberry pi boots succesfully! I know this because ive installed an rdp server via putty and can now remote desktop into it, its running like a charm. The problem however is composit video through the new 3.5mm jack. I have to cables from jack to tulip. One of which only shows black and white, and very blurry video. The other one just shows weird fragments.

I have tried everything regarding the config.txt. I am using an old PAL tv, so i set the sdtv_mode to 2, and aspect ratio to 4:3

my tvservice -s shows state 0x80002 [PAL 4:3], 720x576 @ 50.00Hz, interlaced

Does anyone know how this is possible?

Nils

Image
My guess would be your jack to plugs converter uses the wrong sleeve assignments on the jack. You need one that is Apple Video iPod compatible - yours may not be (but difficult to tell without testing).

There's some stuff in the Q&A thread on this...http://www.raspberrypi.org/forums/viewt ... 75#p577977
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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 2:06 pm

I tried a couple of four pole jacks.

One produced wavy out of sync video if I plugged the audio left, audio right, or composite plugs into my Easycap composite input.

The other produced nothing if I plugged in audio left or composite but worked properly if I plugged the audio right output into the composite video input of the Easycap.

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 2:16 pm

The first thing that must be correct using any of the 3.5mm TRRS adapters is the ground ring position.

With RCA sockets disconnected, 3.5mm jack plugged in and the Pi powered off, measure the resistance using a multimeter between the USB connector shell and the outer ring of the yellow RCA socket on the adapter cable.

If you get a good reading (<1 ohm), then switch the Pi on and probe each of the RCA sockets using the TV's yellow connection. Video should pop up on the TV when the video line is connected to the correct socket.

Audio L/R can then be connected to the remaining 2 sockets. If the channels are swapped, then swap the audio connections.
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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 3:15 pm

Hmm i tried three different cables now, each one gives a different result but none work as they should. Unfortunately i dont have the equipment to check voltages etc. I'm gonna try it on a third, more modern tv to see if that works. thanks for the help so far

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 3:31 pm

Composite with wavy lines sounds like a broken / intermittent ground signal on the yellow composite port.
Since ground path is also provided for left and right channels it's possible that a) the 4 pole jack is dirty or b) the ground and video signal pins are swapped on the cable i.e. not compatible.

Does playing audio via the TV sound normal stereo, or weird with buzzing effect??

Richard S.

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 4:59 pm

redhawk wrote:Composite with wavy lines sounds like a broken / intermittent ground signal on the yellow composite port.
Since ground path is also provided for left and right channels it's possible that a) the 4 pole jack is dirty or b) the ground and video signal pins are swapped on the cable i.e. not compatible.

Does playing audio via the TV sound normal stereo, or weird with buzzing effect??

Richard S.
If that was in response to my post I only use a reversing mirror display and it works fine with the second plug I found.

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 5:40 pm

redhawk wrote:Composite with wavy lines sounds like a broken / intermittent ground signal on the yellow composite port.
Since ground path is also provided for left and right channels it's possible that a) the 4 pole jack is dirty or b) the ground and video signal pins are swapped on the cable i.e. not compatible.

Does playing audio via the TV sound normal stereo, or weird with buzzing effect??

Richard S.
It actually sounds realy good, the audio. The best scenario i've found so far is with one cable, the red rca connector in the video input gives a working video signal. Except its black and white and blurry to the point its unreadable. Yellow and white go in l and r audio, which works fine.

I've also tried it just now on a modern hdtv and the result is the same. HDMI worked perfectly, but sadly isn't an option.

Edit: Although audio sounds realy good, it is very very soft
Last edited by nilsk123 on Thu Jul 17, 2014 5:58 pm, edited 1 time in total.

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 5:53 pm

nilsk123 wrote:It actually sounds realy good, the audio. The best scenario i've found so far is with one cable, the red rca connector in the video input gives a working video signal. Except its black and white and blurry to the point its unreadable. Yellow and white go in l and r audio, which works fine.
In that case you're feeding a NTSC signal into a PAL TV or a PAL signal into an NTSC TV.
Try changing sdtv_mode in /boot/config.txt

Code: Select all

sdtv_mode=0    Normal NTSC
sdtv_mode=1    Japanese version of NTSC – no pedestal
sdtv_mode=2    Normal PAL
sdtv_mode=3    Brazilian version of PAL – 525/60 rather than 625/50, different subcarrier
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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 5:58 pm

I have attached the correct video pinouts. Not all cables are alike and you will very different results by using the incorrect cables.

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Attachments
av-pinouts.jpg
av-pinouts.jpg (51.55 KiB) Viewed 12373 times

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 5:59 pm

DougieLawson wrote:
nilsk123 wrote:It actually sounds realy good, the audio. The best scenario i've found so far is with one cable, the red rca connector in the video input gives a working video signal. Except its black and white and blurry to the point its unreadable. Yellow and white go in l and r audio, which works fine.
In that case you're feeding a NTSC signal into a PAL TV or a PAL signal into an NTSC TV.
Try changing sdtv_mode in /boot/config.txt

Code: Select all

sdtv_mode=0    Normal NTSC
sdtv_mode=1    Japanese version of NTSC – no pedestal
sdtv_mode=2    Normal PAL
sdtv_mode=3    Brazilian version of PAL – 525/60 rather than 625/50, different subcarrier
I just wish it was that simple :) none of the video modes work. as they should. I have a pal tv, and am currently running a pal signal into it (tvservice -s confirms it)

this is my config:

arm_freq=850
core_freq=375
force_turbo=1
gpu_mem=128
disable_overscan=1
start_file=start_x.elf
fixup_file=fixup_x.dat
hdmi_ignore_cec_init=1
sdtv_mode=2
sdtv_aspect=1

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 6:20 pm

What happens to your TV picture when only the video connector is plugged in??

Btw: red should not produce a video signal that is usually assigned for the right audio channel (or left if the solderer can't be bothered to check his wiring for red and white).
Fuzziness sounds like the ground path isn't true this maybe degrade the chromatic signal enough for the TV to switch into monochrome mode.

If you have a digital multimeter in resistance mode (2000 - 200 mode) could you check and make sure the 4 poles as shown by previous poster the match the red, white and yellow connectors.

Richard S.

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 6:24 pm

redhawk wrote:What happens to your TV picture when only the video connector is plugged in??

Btw: red should not produce a video signal that is usually assigned for the right audio channel (or left if the solderer can't be bothered to check his wiring for red and white).
Fuzziness sounds like the ground path isn't true this maybe degrade the chromatic signal enough for the TV to switch into monochrome mode.

If you have a digital multimeter in resistance mode (2000 - 200 mode) could you check and make sure the 4 poles as shown by previous poster the match the red, white and yellow connectors.

Richard S.
With only video plugged in (which is red in my case..) it just shows the fuzzy black n white picture, just like when audio is plugged in aswell. Unfortunately i dont have any equipment to measure resistance.

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 6:28 pm

If you touch the metal parts of the Pi or touch the underside of the A/V socket where it's soldered do you see any variation in the fuzziness??

Richard S.

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 6:33 pm

redhawk wrote:If you touch the metal parts of the Pi or touch the underside of the A/V socket where it's soldered do you see any variation in the fuzziness??

Richard S.
no difference. what puzzles me is that i now have 3 different cables and they all behave differently. they can not all have different pinouts can they?

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 6:57 pm

Unless you have some way of testing the cable then anything discussed here is going to be speculation and theories.
From what I do know dealing with video equipment fuzzy images is usually a sign of a badly degraded signal or with strong interference, maybe you have a faulty SoC or faulty incompatible cable.

Have you tested the TV with other video composite capable devices like a DVD player or VHS recorder??

Have you tried using another power supply for the Pi??

Richard S.

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Re: Trouble with video over 3.5mm jack with B+

Thu Jul 17, 2014 10:12 pm

Pi_Fanatic wrote:I have attached the correct video pinouts. Not all cables are alike and you will very different results by using the incorrect cables.

Pi_Fanatic
I think the Left/Right audio swap is only temporary. If you look at this Raspberry Pi Firmware update on github.
firmware: bplus: Invert left/right channels for pwm audio on bplus

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Re: Trouble with video over 3.5mm jack with B+

Fri Jul 18, 2014 10:02 am

redhawk wrote:Unless you have some way of testing the cable then anything discussed here is going to be speculation and theories.
From what I do know dealing with video equipment fuzzy images is usually a sign of a badly degraded signal or with strong interference, maybe you have a faulty SoC or faulty incompatible cable.

Have you tested the TV with other video composite capable devices like a DVD player or VHS recorder??

Have you tried using another power supply for the Pi??

Richard S.
I have tested the tv with other composite devices such as videogame consoles and they all work fine. I also just tried 2 other power supplies and they both produce the same result.

Having ruled out the cable (tried 3 different ones), the PSU (3 different ones aswel) and the TV (3 different ones aswel), would it be reasonable to assume i have a faulty raspberry pi?

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Re: Trouble with video over 3.5mm jack with B+

Fri Jul 18, 2014 10:27 am

You'd need to have used a definitely compatible 4 pole jack plug before you could blame the Pi.

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Re: Trouble with video over 3.5mm jack with B+

Fri Jul 18, 2014 10:35 am

Having ruled out the cable (tried 3 different ones), the PSU (3 different ones aswel) and the TV (3 different ones aswel), would it be reasonable to assume i have a faulty raspberry pi?
With four wires there are potentially 24 different wiring schemes possible, of which only one will be 100% correct.

So no, unless you can actually measure the cable and confirm the connections are correct you should expect that all three the cables you are using are wired incorrectly!

Most importantly the GND signal (connected to the outer shells of all the RCA connectors) should be connected to the the "ring" nearest to the sleeve of the four pole connector. Without the correct GND wiring no correct video or audio output is possible, but WITH the GND wiring correct its possible to simply switch around the RCA connectors to correct for any wiring differences.

The PI actually uses one of the most often used wiring schemes, as used by Ipods and zunes, but its completely possible that if you have a dozen random four pole to RCA adapters (or cables) none of them will use the "iPod" standard!

If you look at the picture av-pinouts.jpg, you will notice that three of the four described wiring schemes have at least GND on Pin 2, which makes them at least usable, but all the cables that use from one of these "Archos, gigabit, creative Zen, Vision Series, Crown iAudio, and apple iBook" have the wiring scheme that puts GND on Pin 1 instead of Pin 2!, and for the video signal that means that the signal received will have Video and GND reversed, so the signal will actually be inversed (negative).

That's the bad news, the good news that cables using any of the other wiring schemes are either (nearly) perfect, or at least usable! The only difference between an original iPod cable and a PI seems to be that left and right audio channels are interchanged, perhaps this can be solved with software (which detects Composite video is used then exchanges the audio channels), but you can also simply swap the red and white RCA plugs if you care about that.

As for a standard camcorder cable, that can be used too simply by exchanging the right and video RCA connectors, that is the yellow and the red one!

Actually the PI's wiring scheme makes more sense than the iPod ones, as when you ignore the video signal you can simply plug in a three pins (TRS) plug for audio, and GND left and right signal will be correct. The PI correctly uses the tip for the left audio signal, not the right audio signal ( a memory help is that "Right" and "Ring" both start with the same letters). The fact that the video signal will be shorted to GND is of no concern as the designers have taken measures to make that possible without any problem.

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Re: Trouble with video over 3.5mm jack with B+

Fri Jul 18, 2014 10:59 am

When you connect an earphone the video and ground are shorted, but this perhaps works but might lead to higher current consumption. The R-Pi seems to be able to detect if composite video is used and could perhaps turn it off and fix the order of the speakers.
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Re: Trouble with video over 3.5mm jack with B+

Fri Jul 18, 2014 11:22 am

mahjongg wrote:
Having ruled out the cable (tried 3 different ones), the PSU (3 different ones aswel) and the TV (3 different ones aswel), would it be reasonable to assume i have a faulty raspberry pi?
With four wires there are potentially 2^4 = 16 different wiring schemes possible, of which only one will be 100% correct.

So no, unless you can actually measure the cable and confirm the connections are correct you should expect that all three the cables you are using are wired incorrectly!
It's 24 different combinations, actually - 4 permutated in 4 locations.

Code: Select all

   4!
--------
(4 - 4)!
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Re: Trouble with video over 3.5mm jack with B+

Fri Jul 18, 2014 11:30 am

Ah, yes, I was indeed doubting whether my guess it was 2^4 was correct.

Could have know it involved a Factorial operation!

I stand corrected and have edited in the correct number.

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Re: Trouble with video over 3.5mm jack with B+

Fri Jul 18, 2014 11:41 am

mob-i-l wrote:When you connect an earphone the video and ground are shorted, but this perhaps works but might lead to higher current consumption. The R-Pi seems to be able to detect if composite video is used and could perhaps turn it off and fix the order of the speakers.
It certainly works, because the designers made sure of that.
Its true that it could use up a small amount of extra current, but according to my calculations it would only be about 2 or 3 mA (an average of about 6.6 mA injected into the 75 Ohm video input, but from a core voltage of just 1.8Volt, translates to 2 or 3mA from the 5V due to the use of efficient switchers).

shutting off the video when using HDMI video is already done, and as I said before switching the audio channels when generating composite video is a good idea.

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Re: Trouble with video over 3.5mm jack with B+

Fri Jul 18, 2014 11:42 am

alright, so could anyone point me to a cable that should definetly work?

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