Tv-out Disappointments ....


Lazrhog

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So, I finally sorted myself out an extension cable to let me use the TV-out cable (another 10 quid). The TV-out cable I have is one of the supposedly good ones from GBAX.

Anyway, when it is plugged in, any slight movement in the cable where it is connected to the GP2X, results in the picture becoming black and white. I had heard some murmerings on the forum about connector issues, but thought that was only with the poor quality ones.

Secondly, when playing video, the update rate of the video on the TV appears to be half that of what it is on the GP2X. Anyone else had this (Firmware 1.4) ? It shouldn't be an encoding thing, as the video is fine when just viewed on the GP2X.


I am really gutted, as playing DivX on the TV was one of the reasons I bought the GP2X in the first place...... all I am left with is jerky looking video flicking between black and white and colour !
 

WhizzBang

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I also bought my cable from GBAX and I do not have any of the problems you are seeing. The picture is always fine for me and I have not noticed any difference in framerate from using the LCD screen. Maybe your cable is defective?
 

nickspoon

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Yeah, you should try returning your cable. Mine is also fine and I get a perfect picture, even with video. The flicking between black and white and colour means there is a dodgy connection somewhere and your TV isn't detecting the S-Video signal properly. Check all your cables first, and if you can't see any problems, return the TV-Out cable.
 

icurafu

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I never really bothered with the TV-out function but, isn't the movie player on tv-out outputted to a much higher resolution?

That would mean more processing. This may be to do with the compression quality and format of the movie you have chosen. Try encoding your movies to lower quality compression.

You could also try overclocking before you play on a TV to see if that improves the smoothness.
 

nickspoon

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The image-scaling for TV-Out isn't done by the main cores, it's done by a CX scaler chip; that's why it was put in. It doesn't affect the speed of the video output at all.
 

Lazrhog

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icurafu posted on Apr 9 2006 at 11:08 AM said:
I never really bothered with the TV-out function but, isn't the movie player on tv-out outputted to a much higher resolution?

That would mean more processing. This may be to do with the compression quality and format of the movie you have chosen. Try encoding your movies to lower quality compression.

You could also try overclocking before you play on a TV to see if that improves the smoothness.

Ahh, didn't try overclocking. The format of the video is HDTV, so it is well over the top, but the GP2X plays it perfectly (LOST Season2 - fantastic by the way :)) Perhaps I will re-encode it to an NTSC Resolution and try that.
 
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Aninhumer

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nickspoon posted on Apr 9 2006 at 12:19 PM said:
The image-scaling for TV-Out isn't done by the main cores, it's done by a CX scaler chip; that's why it was put in. It doesn't affect the speed of the video output at all.
Yeah, but the scaler chip can't decode videos.
The processor could be strained by a 720*480 video?
 
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nickspoon

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The video decoding is not done by the processors. There is separate specialised video decoder hardware to handle that. It will only decode DivX, XviD, MPEG-4, MPEG-2, MJPEG and H.263, however. All mplayer does is throw data at the video decoder, which, in TV-Out mode, sends it to the CX chip to be scaled, then sends it to the TV.
 

Aninhumer

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How fast is the decoder chip? If it was originally designed to work with 320*240 videos it might not be powerful enough to handle higher resolutions, but seeing as GPH designed the gp2x with TV-out in mind I rather doubt that.

I thought the video chip only helped to decode things at a basic level, and I certainly didn't know it could handle that many codex.
 

nickspoon

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The decoder chip was originally designed to decode MPEG-4 at a resolution of 1024*768, so it can easily decode anything lower and any of the other codecs I listed. The video decoding system is actually made from three sections: the preprocessor, the scaler, and the postprocessor.
 

Aninhumer

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I know, that's why I thought it only handled the bits that are the same for all of them, letting the software handle the difference.
 

Lazrhog

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Hmm, just went and tried it again, and it worked flawlessly. I wonder if I just made a bad connection somewhere ? Really strange.

Oh well. Case closed.

Thanks for the replies.
 
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