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by karlkiste
Mon Oct 14, 2013 8:53 am
Forum: Graphics, sound and multimedia
Topic: Can I use a 4.3" LCD with Pi?
Replies: 7
Views: 2368

Re: Can I use a 4.3" LCD with Pi?

The good thing is, you don't need EDID on the pi, you can set a fixed resolution in config.txt. This is most useful when the pi is hard-wired to a certain display. When booting, the kernel sets a framebuffer graphics mode (the pi has no native text modes afaik). X will just use that mode, it will no...
by karlkiste
Thu Sep 05, 2013 4:59 am
Forum: Graphics, sound and multimedia
Topic: USB capture card
Replies: 1
Views: 1287

Re: USB capture card

Most devices today use UVC (USB Video Class), and should therefore work on about any linux system.

To be sure, check here:

http://www.ideasonboard.org/uvc/
by karlkiste
Tue Sep 03, 2013 7:11 am
Forum: Graphics, sound and multimedia
Topic: Real-time playback from microphone is delayed, solutions?
Replies: 5
Views: 3311

Re: Real-time playback from microphone is delayed, solutions

I'm no sound expert, but from my knowledge about computers and electronics I would say: For low-latency realtime effects, input and output must be on a single "device". The same clock source must be used for input and output. This is the only way to ensure that the clocks will not get out of sync. I...
by karlkiste
Mon Sep 02, 2013 12:26 pm
Forum: Graphics, sound and multimedia
Topic: adding a speaker
Replies: 12
Views: 9914

Re: adding a speaker

But it hasn't changed since the first version, so maybe the designer knows more than me? I presume, the problem is - that it works :-) It was never meant to be approved by hifi-freaks who claim to hear a difference between speaker cables made from copper and those made from silver. I think it is a ...
by karlkiste
Sun Sep 01, 2013 5:08 pm
Forum: Graphics, sound and multimedia
Topic: adding a speaker
Replies: 12
Views: 9914

Re: adding a speaker

Though, since the 0 - 3v3 swing of the (PWM) audio is devided down by the potential devider to only 1v p-p, and therefore only go ±0.5v, those diodes won't have much effect. This explanation had made more sense to me, if both the anodes and the cathodes had been connected to GND. Then the swing wou...
by karlkiste
Sun Sep 01, 2013 12:15 pm
Forum: Graphics, sound and multimedia
Topic: adding a speaker
Replies: 12
Views: 9914

Re: adding a speaker

The output impedance of the Pi's analog audio out is more than 100 Ohm. Connected to a 8 Ohm speaker, you might get something like 0,5 milliwatts. I dare say, this is barely audible. But, suggesting a 25 watts amplifier to have a beeping hand-held device is a bit too much, I think. Looking at the po...
by karlkiste
Sun Sep 01, 2013 6:48 am
Forum: Graphics, sound and multimedia
Topic: Espeak sounds slow and broken
Replies: 30
Views: 19978

Re: Espeak sounds slow and broken

output of

espeak -s 5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa...

Samples are shown from the start of the sound output and a few seconds later.
by karlkiste
Sun Sep 01, 2013 5:20 am
Forum: Graphics, sound and multimedia
Topic: Espeak sounds slow and broken
Replies: 30
Views: 19978

Re: Espeak sounds slow and broken

It is not like "espeak speaks too slow". It's like it speaks correctly for several seconds, then suddenly between groups of speech samples, a gap appears and the sound "stutters". All speech samples are played, so, due to the gaps, the speech appears stretched or slow. It is not a matter of taste fo...
by karlkiste
Sat Aug 31, 2013 4:14 pm
Forum: Graphics, sound and multimedia
Topic: Rpi Video Wall
Replies: 18
Views: 9358

Re: Rpi Video Wall

I've done something similar, but not quite the same. I've modified omxplayer, so it won't start until a certain GPIO has a "high" level. This check is done after all the initializations, right before the first video frame is displayed. It is checked in a fast spinning loop to get a quick startup. Th...
by karlkiste
Sat Aug 31, 2013 3:29 pm
Forum: Graphics, sound and multimedia
Topic: Espeak sounds slow and broken
Replies: 30
Views: 19978

Re: Espeak sounds slow and broken

It must be a problem of connecting to the sound system. This way it works fine:

espeak -f longtext.txt --stdout | aplay

Reads for several minutes now without stuttering.

Greets,
Kiste
by karlkiste
Wed Jun 26, 2013 9:43 am
Forum: Graphics, sound and multimedia
Topic: Click noise when starting analog audio sound playback
Replies: 18
Views: 18830

Re: Click noise when starting analog audio sound playback

I've come to check again yesterday, and I found that with the latest raspbian image, the problem seems to be solved. Probably the sound module, once used, stays active and therefore the clicking is gone. Only after booting, when sound is used for the first time, there is a single click, which is acc...
by karlkiste
Fri May 17, 2013 7:14 am
Forum: Raspbian
Topic: "fake" overscan compensation
Replies: 2
Views: 1753

Re: "fake" overscan compensation

have a look at overscan.c in https://github.com/ukscone/set_overscan Thank you! This solves this particular problem indeed. It is of course a raspberry-only solution ;-) This problem could arise with other hardware setups, so if anyone has an additional idea how to reduce only the USED size of the ...
by karlkiste
Thu May 16, 2013 9:52 am
Forum: Raspbian
Topic: "fake" overscan compensation
Replies: 2
Views: 1753

"fake" overscan compensation

Hi! I'm using disable_overscan=1 in config.txt with a display which in fact does do overscan, and I need to do so. This way the framebuffer fills the whole screen like videos played by omxplayer do. If I'd set disable_overscan=0, the framebuffer would be noticeable smaller than the video window. I c...
by karlkiste
Sun Apr 28, 2013 4:10 pm
Forum: General discussion
Topic: When will the next batch of Model A be available?
Replies: 5
Views: 1349

Re: When will the next batch of Model A be available?

Strange... A few clicks deeper in the farnell site, they suddenly say they had plenty of A's. So perhaps my concern is pointless for now ;-)

Greets,
Kiste
by karlkiste
Sun Apr 28, 2013 11:37 am
Forum: General discussion
Topic: When will the next batch of Model A be available?
Replies: 5
Views: 1349

Re: When will the next batch of Model A be available?

Thank you, good to know. But I'd prefer to pay in euro, as I'd use them commercially. My last order was 250 pieces, and I might need another 500 soon, so even if newit only adds two pounds to the RS price, it is quite a sum altogether. Sure, if I really need those additional model a's, I'll go and b...
by karlkiste
Sun Apr 28, 2013 8:40 am
Forum: General discussion
Topic: When will the next batch of Model A be available?
Replies: 5
Views: 1349

When will the next batch of Model A be available?

Farnell says, model A is out of stock. RS is just selling the last couple these days, giving no date for fresh supplies.

Is there another batch of Model A in production or planned? When will it be available again?

Greets,
Kiste
by karlkiste
Wed Feb 27, 2013 4:53 pm
Forum: Graphics, sound and multimedia
Topic: omxplayer patch: Where to send to?
Replies: 4
Views: 926

Re: omxplayer patch: Where to send to?

Either submit a pull request (see https://help.github.com/articles/using-pull-requests ) or open a new issue where you describe the problem (and suggested solution). Ah... ok... It is quite certain that these two lines are all I will ever have to contribute to this piece of software. I'm not feelin...
by karlkiste
Wed Feb 27, 2013 3:36 pm
Forum: Graphics, sound and multimedia
Topic: omxplayer patch: Where to send to?
Replies: 4
Views: 926

Re: omxplayer patch: Where to send to?

Thanks, this is where I got the source code from. But I found no email address to contact someone there, this is why I posted this question.
by karlkiste
Wed Feb 27, 2013 8:04 am
Forum: Graphics, sound and multimedia
Topic: Click noise when starting analog audio sound playback
Replies: 18
Views: 18830

Re: Click noise when starting analog audio sound playback

A potential solution to improve the general sound quality would be to enable a higher sampling rate (88200 ks/s or higher) Actual driver does not allow this. Would anyone know where the limitiation comes from? Hardware or just not implemented as sound quality was assumed not to be important? It's p...
by karlkiste
Wed Feb 27, 2013 7:42 am
Forum: Graphics, sound and multimedia
Topic: omxplayer patch: Where to send to?
Replies: 4
Views: 926

omxplayer patch: Where to send to?

Hi! I'm controlling omxplayer through a named pipe. It's a bit annoying that only one command is possible per video frame. If multiple commands are sent at once, they will not be executed at best, but it could also lead to a buffer overrun and kick the player (or worse). So I cannot mute the sound b...
by karlkiste
Thu Feb 14, 2013 5:43 am
Forum: General programming discussion
Topic: SPI between two RPi's
Replies: 10
Views: 4295

Re: SPI between two RPi's

So no sync, so no data. i did tat pairing and im able to receive @101KB/s(maximum). Did you check the data? It may well be that you did receive something, and if you've been transmitting /dev/zero you might even "see" "correct" data. Transfer real data, and check for integrity. The SPI master canno...
by karlkiste
Thu Feb 14, 2013 5:33 am
Forum: General programming discussion
Topic: Is "bash script" a relevant language?
Replies: 25
Views: 3042

Re: Is "bash script" a relevant language?

joan wrote:
karlkiste wrote:You'll get an impressive 36 Mbps if you raise the clock to 950THz.
Oh, that's too dangerous for my taste. The electromagnetic noise which is radiated from the PCB traces will be in the far ultraviolet, X-ray or gamma spectrum. I'll wait for a lead-cast case for the Pi before trying that ;-)
by karlkiste
Wed Feb 13, 2013 7:22 pm
Forum: General programming discussion
Topic: Is "bash script" a relevant language?
Replies: 25
Views: 3042

Re: Is "bash script" a relevant language?

Concerning the drawbacks when programming bash: I've wrote a bitbanging SPI master transmitter (without receive). It can transfer incredible 36 bits per second with 950MHz overclocking :-D (The real problem is probably not bash itself, but there are five or so programs loaded, executed and terminate...
by karlkiste
Wed Feb 13, 2013 9:08 am
Forum: General programming discussion
Topic: SPI between two RPi's
Replies: 10
Views: 4295

Re: SPI between two RPi's

[email protected] wrote: (or serial for slower speeds)
"Slower speeds" are up to 1 megabit. The uart itself can easily do 4MBit and more, but the CPU will struggle to even store the data on a ramdisk in time. If you're employing hardware handshake (rts/cts), you may transmit 4MBit via uart without a problem.
by karlkiste
Wed Feb 13, 2013 9:02 am
Forum: General programming discussion
Topic: SPI between two RPi's
Replies: 10
Views: 4295

Re: SPI between two RPi's

As both are masters can i connect MOSI(RPi1)-MISO(RPi2) n MOSI(RPi2)-MISO(RPi1) ? You can do that without danger of damaging anything - and without the possibility to transmit data ;-) The master is the one who generates the clock signal, and a slave inputs and outputs data at the edges of this clo...

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