dhrv
12th August 2008, 17:53
hello,
i have a X-Fi XtremeMusic with analog connected 7.1 speakers (Teufel Concept G) and everything is working fine, i'm just curious about some things:
1. is the DD/DTS decoding of the X-Fi done via hardware or software? i ran a test (ffdshow ac3 decoding vs. x-fi ac3 decoding) and in both cases the CPU usage was the same! so i guess the X-Fi has no hardware decoding?! (plus in the creative directory there are some dts+ac3 .dll and .ax files)
2. is there a formula to determine the optimal crossover frequency for my 7.1 set? my manufacturer says 120hz and THX, which licensed this 7.1 set, says 135hz. so who to believe?!
3. my X-Fi decodes most 6ch ac3 streams as Dolby Digital but some streams are decoded as Dolby Digital EX. the ones which are decoded as DDex have a "bitstream=8" flag in virtualdub's stream list. the normal Dolby Digital streams only have "bitstream=6". since DDex doesn't contain a discrete back surround channel i wondered if it's possible to maybe rewrite the header of an ac3 stream from bitstream=6 to bitstream=8 so that my X-Fi decodes it as DDex?
the only reason i want to do this is because the X-Fi itself is not capable of upmixing 5.1 to 7.1. the only thing it does is copying the surround channels of the 5.1 stream to the side speakers. so an explosion that is actually behind me suddenly explodes next to me, too. with Dolby Digital EX the surround sound is more like it's supposed to be, but still, i have a 7.1 set and want to use it! that's why i made a lot of custom matrices in ffdshow, e.g. a side channel that consists of 60% surround channel and 40% front channel. it sounds okay but not great and i have no phase shift at all. Dolby Pro Logic or PLII use some +-90 degree phase shifts to make the rear channels sound better....so now my final question: is there a website that provides 5.1->7.1 upmix matrices? or is there any setting in AC3filter? or something else i haven't thought of?
thanks a lot and please correct me if i made any mistakes, i'm not an expert like you guys :)
dhrv
i have a X-Fi XtremeMusic with analog connected 7.1 speakers (Teufel Concept G) and everything is working fine, i'm just curious about some things:
1. is the DD/DTS decoding of the X-Fi done via hardware or software? i ran a test (ffdshow ac3 decoding vs. x-fi ac3 decoding) and in both cases the CPU usage was the same! so i guess the X-Fi has no hardware decoding?! (plus in the creative directory there are some dts+ac3 .dll and .ax files)
2. is there a formula to determine the optimal crossover frequency for my 7.1 set? my manufacturer says 120hz and THX, which licensed this 7.1 set, says 135hz. so who to believe?!
3. my X-Fi decodes most 6ch ac3 streams as Dolby Digital but some streams are decoded as Dolby Digital EX. the ones which are decoded as DDex have a "bitstream=8" flag in virtualdub's stream list. the normal Dolby Digital streams only have "bitstream=6". since DDex doesn't contain a discrete back surround channel i wondered if it's possible to maybe rewrite the header of an ac3 stream from bitstream=6 to bitstream=8 so that my X-Fi decodes it as DDex?
the only reason i want to do this is because the X-Fi itself is not capable of upmixing 5.1 to 7.1. the only thing it does is copying the surround channels of the 5.1 stream to the side speakers. so an explosion that is actually behind me suddenly explodes next to me, too. with Dolby Digital EX the surround sound is more like it's supposed to be, but still, i have a 7.1 set and want to use it! that's why i made a lot of custom matrices in ffdshow, e.g. a side channel that consists of 60% surround channel and 40% front channel. it sounds okay but not great and i have no phase shift at all. Dolby Pro Logic or PLII use some +-90 degree phase shifts to make the rear channels sound better....so now my final question: is there a website that provides 5.1->7.1 upmix matrices? or is there any setting in AC3filter? or something else i haven't thought of?
thanks a lot and please correct me if i made any mistakes, i'm not an expert like you guys :)
dhrv