| Any chance of .img.ecm and compressed file support anytime soon? [message #4087] |
Sun, 19 July 2015 19:37  |
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eg, through libmirage or something like that.
I know that pcsxr has both, but i found some worrying things about their ecm support.
Namely, it only works in most games if you use the simulate bios option and even then it often hangs loading during in-game disc changes.
Do you think you can do better?
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| Re: Any chance of .img.ecm and compressed file support anytime soon? [message #4088 is a reply to message #4087 ] |
Mon, 20 July 2015 01:27  |
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ECM is not a compression format and was not intended to be used on its own. It removes regenerateable data to improve the compression ratio when compressed with a proper archive format.
Having a emulator load raw ecm files is silly and instead compression should be done properly.
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| Re: Any chance of .img.ecm and compressed file support anytime soon? [message #4091 is a reply to message #4088 ] |
Mon, 20 July 2015 06:48 |
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Well of course its not a compression format, but it's not silly. At all. It supposed to be used in conjunction with other compression formats. But it still needs to be supported in a emulator in order to not be absurdly painful for its intended purpose.
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| Re: Any chance of .img.ecm and compressed file support anytime soon? [message #4092 is a reply to message #4091 ] |
Mon, 20 July 2015 06:50 |
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Also when there is good cross platform library that makes such a thing easy (and a myriad of other cd formats), i don't know why it's not more common.
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| Re: Any chance of .img.ecm and compressed file support anytime soon? [message #4101 is a reply to message #4088 ] |
Tue, 21 July 2015 16:52 |
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I'll say this: a much better alternative was if 7zip compressor and uncompression library was updated to recognize psx iso/bin - with the SLUS codes or something - and apply ecm compression/uncompression transparently.
So when every emulator updated their lib7z everyone would get it for 'free', plain ecm support deprecated and the compressed iso reading code could be much simplified (hopefully). It would require end user data massaging, but no big deal for cmd line ninjas like us right?
I opened this bug report for it. Depending if it's accepted or closed i might downgrade this request for only 7z compressed image file support since it would then be transparent for the code (but see below).
https://sourceforge.net/p/sevenzip/bugs/1538/
I'll be honest, i only started this topic after finding out pcsxr ecm support shit the bed when trying to change discs (and it only worked with simulated bios anyway). Check these pcsxr bug reports for details:
http://pcsxr.codeplex.com/workitem/12151
http://pcsxr.codeplex.com/workitem/12152
So obviously there are cd timing traps here. There shouldn't be since the entire decompression should have already been done to memory or file before the disc change notification but obviously that's not what is happening. Maybe that is 'unacceptably high latency'? Regardless, i'd ask that if you're implementing compression you think of doing it that way to avoid race conditions in crappy psx game code. Or maybe you have a better solution.
I can't find mednafen bug report page otherwise i'd just dump all this information there, hope you don't mind.
[Updated on: Tue, 21 July 2015 17:43]
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