Comments for Hardwarebug http://hardwarebug.org Everything is broken Mon, 30 Aug 2010 09:33:38 +0000 hourly 1 http://wordpress.org/?v=3.0.1 Comment on Countryside by lu_zero http://hardwarebug.org/2010/08/17/countryside/comment-page-1/#comment-1230 lu_zero Mon, 30 Aug 2010 09:33:38 +0000 http://hardwarebug.org/?p=541#comment-1230 Wonderful pictures and places. Where are them? Wonderful pictures and places. Where are them?

]]> Comment on IJG swings again, and misses by Mans http://hardwarebug.org/2010/02/01/ijg-swings-again-and-misses/comment-page-1/#comment-1229 Mans Thu, 26 Aug 2010 12:20:14 +0000 http://hardwarebug.org/?p=234#comment-1229 The tests I performed used the settings suggested in the manual, downscaling on encode and upscaling on decode. The tests I performed used the settings suggested in the manual, downscaling on encode and upscaling on decode.

]]> Comment on IJG swings again, and misses by Ben R-G http://hardwarebug.org/2010/02/01/ijg-swings-again-and-misses/comment-page-1/#comment-1227 Ben R-G Wed, 25 Aug 2010 20:36:48 +0000 http://hardwarebug.org/?p=234#comment-1227 I don't think this IJG has much to do with the IJG of the 1990s. Tom Lane (the former organizer of the IJG) was not involved in v7 and later releases as far as I know. I think they're almost solely the work of Guido Vollbeding, who does seem to be a bit kooky. I think you've missed the point of "SmartScale". As far as I can tell, the idea is to use smaller block sizes than 8x8. You can simulate this in the v7 library by scaling by 8/n on encode, with n less than 8, then scaling by n/8 on decode (you can even simulate it in version 6b with n=1,2,4). "SmartScale" stores the n/8 factor in the file so it can be automatically applied when decoding, kind of like EXIF rotation, and also suppresses the AC coefficients that are always zero. It doesn't add support for larger DCTs with more than 64 outputs; when you scaled by 8/n with n greater than 8 you simply lost the high-frequency components with predictable results. There is an ITU-T recommendation, T.851, which adds 16-bit samples and a new arithmetic coding mode to T.81. I had assumed that the promised improvements in v8 would be an implementation of that standard, but apparently not. I don’t think this IJG has much to do with the IJG of the 1990s. Tom Lane (the former organizer of the IJG) was not involved in v7 and later releases as far as I know. I think they’re almost solely the work of Guido Vollbeding, who does seem to be a bit kooky.

I think you’ve missed the point of “SmartScale”. As far as I can tell, the idea is to use smaller block sizes than 8×8. You can simulate this in the v7 library by scaling by 8/n on encode, with n less than 8, then scaling by n/8 on decode (you can even simulate it in version 6b with n=1,2,4). “SmartScale” stores the n/8 factor in the file so it can be automatically applied when decoding, kind of like EXIF rotation, and also suppresses the AC coefficients that are always zero. It doesn’t add support for larger DCTs with more than 64 outputs; when you scaled by 8/n with n greater than 8 you simply lost the high-frequency components with predictable results.

There is an ITU-T recommendation, T.851, which adds 16-bit samples and a new arithmetic coding mode to T.81. I had assumed that the promised improvements in v8 would be an implementation of that standard, but apparently not.

]]> Comment on Hacking the Popcorn Hour C-200 by ANSI FATE | Breaking Eggs And Making Omelettes http://hardwarebug.org/2010/05/03/hacking-the-popcorn-hour-c-200/comment-page-1/#comment-1225 ANSI FATE | Breaking Eggs And Making Omelettes Tue, 24 Aug 2010 05:55:57 +0000 http://hardwarebug.org/?p=479#comment-1225 [...] list. This one reports itself as running on 74kf CPU. Googling for this processor quickly brings up Mans’ post about the Popcorn Hour device. So, congratulations to him for getting the mundane box to serve a higher purpose. Perhaps one day, [...] [...] list. This one reports itself as running on 74kf CPU. Googling for this processor quickly brings up Mans’ post about the Popcorn Hour device. So, congratulations to him for getting the mundane box to serve a higher purpose. Perhaps one day, [...]

]]> Comment on ARM inline asm secrets by Stian Skjelstad http://hardwarebug.org/2010/07/06/arm-inline-asm-secrets/comment-page-1/#comment-1193 Stian Skjelstad Sat, 31 Jul 2010 19:22:02 +0000 http://hardwarebug.org/?p=493#comment-1193 Using undocumented features that might change in future gcc versions isn't pure evil as some people claim. If you need some fancy features in an project you are working on, you probably lock down which versions of libraries and tools-chains that you work on. Jumping for gcc3.x to gcc4.x for instance is normally not recommended in a live project, especially in the embedded world Using undocumented features that might change in future gcc versions isn’t pure evil as some people claim.

If you need some fancy features in an project you are working on, you probably lock down which versions of libraries and tools-chains that you work on. Jumping for gcc3.x to gcc4.x for instance is normally not recommended in a live project, especially in the embedded world

]]> Comment on Hacking the Popcorn Hour C-200 by Mans http://hardwarebug.org/2010/05/03/hacking-the-popcorn-hour-c-200/comment-page-1/#comment-1179 Mans Fri, 23 Jul 2010 23:01:31 +0000 http://hardwarebug.org/?p=479#comment-1179 I used latest from git. There are some MIPS fixes there which I don't think have made it into a release yet. I used latest from git. There are some MIPS fixes there which I don’t think have made it into a release yet.

]]> Comment on Hacking the Popcorn Hour C-200 by Andy http://hardwarebug.org/2010/05/03/hacking-the-popcorn-hour-c-200/comment-page-1/#comment-1178 Andy Fri, 23 Jul 2010 13:15:51 +0000 http://hardwarebug.org/?p=479#comment-1178 Thanks, a lot, I've successfully built the kernel. But loading it with kexec userspace tool (latest version from kernel.org, 2.0.1) fails with Invalid memory segment 0x4000000 - 0x42d3fff What kexec binary did you use? Thanks, a lot, I’ve successfully built the kernel. But loading it with kexec userspace tool (latest version from kernel.org, 2.0.1) fails with

Invalid memory segment 0×4000000 – 0x42d3fff

What kexec binary did you use?

]]> Comment on Hacking the Popcorn Hour C-200 by Mans http://hardwarebug.org/2010/05/03/hacking-the-popcorn-hour-c-200/comment-page-1/#comment-1177 Mans Thu, 22 Jul 2010 20:46:06 +0000 http://hardwarebug.org/?p=479#comment-1177 http://www.networkedmediatank.com/download/firmware/nmt/gpl/linux-2.6.22.19.tar.bz2 http://www.networkedmediatank.com/download/firmware/nmt/gpl/linux-2.6.22.19.tar.bz2

]]> Comment on Hacking the Popcorn Hour C-200 by Andy http://hardwarebug.org/2010/05/03/hacking-the-popcorn-hour-c-200/comment-page-1/#comment-1174 Andy Thu, 22 Jul 2010 11:46:38 +0000 http://hardwarebug.org/?p=479#comment-1174 The problem is that Sigma patches are not applicable to 2.6.22.19 kernel sources from linux-mips.org. Patches can be applied to vanilla sources from kernel.org, but kernel config is not suitable there. Also, I'm not sure that mips kernel can possibly be built from sources at kernel.org. Rebuilding firmware kernel is much less preferrable for me. So, what exact sources did you use? The problem is that Sigma patches are not applicable to 2.6.22.19 kernel sources from linux-mips.org. Patches can be applied to vanilla sources from kernel.org, but kernel config is not suitable there.
Also, I’m not sure that mips kernel can possibly be built from sources at kernel.org.

Rebuilding firmware kernel is much less preferrable for me.

So, what exact sources did you use?

]]> Comment on Hacking the Popcorn Hour C-200 by Mans http://hardwarebug.org/2010/05/03/hacking-the-popcorn-hour-c-200/comment-page-1/#comment-1173 Mans Wed, 21 Jul 2010 17:02:10 +0000 http://hardwarebug.org/?p=479#comment-1173 You need the Sigma patches. You need the Sigma patches.

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