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| AC3 RF demodulators are very expensive, any alternative? https://forum.lddb.com/viewtopic.php?f=24&t=9648 |
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| Author: | cplusplus [ 05 Aug 2022, 06:03 ] |
| Post subject: | Re: AC3 RF demodulators are very expensive, any alternative? |
I think it is still a two step process until it is added to ld-decode. There is FPGA code in staffanu's repo which opens the door to new AC-3 RF demodulators or modding players to output the demodulated signal. |
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| Author: | muzer [ 05 Aug 2022, 19:42 ] |
| Post subject: | Re: AC3 RF demodulators are very expensive, any alternative? |
I'm no expert but I'd think at that frequency you'd be better off building a board based around a DSP, no? Much cheaper than an FPGA... |
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| Author: | ohnoyoko [ 06 Aug 2022, 17:10 ] |
| Post subject: | Re: AC3 RF demodulators are very expensive, any alternative? |
cplusplus wrote: I think it is still a two step process until it is added to ld-decode. There is FPGA code in staffanu's repo which opens the door to new AC-3 RF demodulators or modding players to output the demodulated signal. Yeah, it's not properly integrated with the original workflow. I think there are intentions to do that at some point, contingent on the usual open source caveats (time, desire, etc.). But, for now, it is a functioning proof-of-concept. 
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| Author: | drecksoft [ 09 Sep 2022, 09:42 ] |
| Post subject: | Re: AC3 RF demodulators are very expensive, any alternative? |
ohnoyoko wrote: ldfan wrote: ohnoyoko wrote: Seriously, it is now possible to get the AC3 signal from DdD output and, with care, generate video captures that contain the original DD audio. If my understanding of the Doomsday Duplicator is correct, the file that gets extracted would need some kind of hardware/software system designed to mimic how a LaserDisc player works to play the file. Thus, if that is the case, you would still need an AC3-RF Demodulator to once again extract the AC3 signal since it's still encoded unlike any other current playback device we have (e.g.: DVD, Blu ray, broadcast, etc.). Basically, the DdD converts the analog signal from the disc into a raw digital signal. You then have to decode the output (RGB visual data, analog audio, and digital EFM track if it exists), and run further run the output through whatever filters (probably in ffmpeg but it can technically be other programs) are required to produce a final A/V signal your eyes & ears can process. The digital track can also be processed and the data or audio "ripped" somewhat like a CD. I've used it to extract some audio and confirm that the audio is a perfect copy of whatever's on the digital track (or, if the software and/or the disc are janky, where the glitches occur, assuming they can be noticed, which isn't always the case). You could use it to grab the data from LaserActive games but that's another story. I believe all this also works for MUSE discs, although I'm not aware of the current status of MUSE decoding. (If anybody wants to buy me and the DdD devs a MUSE player to mod and play with....) Nice to see you here after your excellent work on AC3RF. Theoretically MUSE capturing should work with the DdD. The bandwidth will be higher than for regular LDs but 40MBps should be more than sufficient. Unfortunately I was unable to get any decently priced (less than 3 digits) MUSE Hi-VIsion discs. I do have a player and a decoder but can't test neither due to the missing disc(s). If I find one, I'll provide a capture file. |
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