What would you do with slow and limited TV out?

[dreamlayers]

I've found one method for TV out on Video iPods, and I've submitted a preliminary patch.  The method I'm using has several limitations:

• If an LCD update command happens while picture data is being output, there will be a few black lines in that field
• TV output stops for a bit while the image is changed
• This method is probably too slow for video

Would you want this in Rockbox, and how would you integrate it into Rockbox?  I'm think it would only be useful for still image viewing and slideshows.

In case you're wondering about why the original firmware can do so much better:  This code is uploading picture data and sending commands to the BCM (the DSP chip which handles the LCD and TV out).  The original firmware runs programs on the BCM, and they do work such as H.264 and AAC-LC decoding or slideshows.  I did not investigate how to do this.  I believe the following is a directory listing of BCM firmware, created by someone else:
http://74.125.95.132/search?q=cache:bZy7xfpGS5UJ:fr.pastebin.ca/1232048

[Chronon]

My 5g iPod is broken at the moment.  But I could see using this functionality for slideshows/presentations.  It would seem to make sense as a viewer plugin, though probably not the default one (i.e. select via context menu).

[dreamlayers]

What about just having an option to use TV out in the JPEG viewer plugin?

[Llorean]

What's the maximum framerate on it (possibly if you disable normal LCD updating while it's active, since apparently that causes graphical glitches?) and does it create much CPU overhead while active, or just bog down the broadcom chip itself?

[Chronon]

What about just having an option to use TV out in the JPEG viewer plugin?

Sure, that sounds fine too.  I'll let others chime in since I can't really take advantage of this at the moment anyway.

[LambdaCalculus]

TV out for the JPEG plugin would be useful. Although the iPod 4G color has TV out as well, that model doesn't have a Broadcom chip in it. I need to look again to see what the 4G color uses for TV out.

[soap]

I'd be more likely to want to display WPS than jpeg.

[dreamlayers]

Regarding frame rates and displaying the WPS, the main problem is that the TV out signal is lost for a short time while switching images.  (And I mean lost; not even sync is output.)  This might be acceptable for slideshows but I don't think it would be acceptable for WPS or video.   

Frame rate is certainly enough for slide shows, even at 720x480.   I'll time it tomorrow.

Finally, here are the benchmarks:

30 Mhz:
320x240, NTSC: 52.5 FPS, 42% CPU
720x480, NTSC: 6.6 FPS, 24% CPU
720x576, PAL: 5.5 FPS, 24% CPU

80 Mhz:
320x240, NTSC: 72 FPS, 21% CPU
720x480, NTSC: 7.7 FPS, 11% CPU
720x576, PAL: 6.4 FPS, 10% CPU

The speed increase at 80 Mhz comes purely from faster loading of data into the BCM.  The amount of time the BCM takes after that is unchanged.

[jswetzen]

I can see the potential of presenting slide shows with a much higher resolution than the OF, if that is possible. 320x240 pixels gets too blurry for serious presentations. Powerpoint-like presentations would also be a possibility, perhaps using something like the WPS syntax for formatting?

[pabouk]

Powerpoint-like presentations would also be a possibility, perhaps using something like the WPS syntax for formatting?

I think that much more feasible would be to convert the slides of the presentation to bitmaps (PNG, BMP...) The already existing image viewer would need just some enhancements to be better suited for presentations.

[dreamlayers]

I found the BCM's TV output frame buffer.  Writes to it allow the image to be updated instantly and without any interruptions in the signal.  This will allow video and more.  See http://www.rockbox.org/tracker/task/9787#comment28147

[Chronon]

Neat.  I wish my 5g wasn't dead.   :'(

[dreamlayers]

Neat.  I wish my 5g wasn't dead.   :'(

Is it dead due to one of the inductors getting ripped off the board?  I've managed to solder one back on even though I had to solder to just a tiny bit of fine wire under the inductor.

[Chronon]

Yes.  That's the one.

Thanks for the encouragement.  I have actually come by a cheap (dead) main board with the inductors on it, so I can have a go this weekend.

[dreamlayers]

Yes.  That's the one.

Thanks for the encouragement.  I have actually come by a cheap (dead) main board with the inductors on it, so I can have a go this weekend.

Great!  That should be an easier and better fix than attaching a ripped off inductor.

On the 30G there are supposed to be rubber pieces around both inductors.  They prevent the HD from slamming into the inductors if the iPod is dropped.  You can add some rubber between the HD and metal frame if you are missing those.