Recording AC3 *a challenge for the best and brightest!*

I am trying to make some DVDs of some laserdiscs I have. Now - my sound card has an SPDIF in, and I wanted to record the AC3 track. I could not do it directly from the RF of the laserdisc player as it is RF. Then I hit upon an idea to hook my Amp up, which has an ac3 rf in and also a standard SPDIF out. Sure enough it worked a treat. The stuff it recorded into a 48khz stereo file WAS Ac3 and could be run back out to thr amp. I recorded it in Sound Forge 4.5 and then saved it as RAW. One thing that was odd was that because it thought it was PCM it left gaps in the audio track - so basically it has the AC3 frames and then space and then the next frame etc. And it is about 3 or 4 times the size it should be. Now THE CHALLENGE! Who knows of a piece of software that will take my RAW file and rebuild the AC3 into a proper AC3 file suitable for burning to dvd WITHOUT recompressing it (obviously after all this I don't want to loose any quality by having to recompress) Can anyone else offer any helpful advice? Surely I cannot be such a "pioneer" ... ;) Cheers, Quilty

1. prboably BeSplit could eat it as 'ddwav'. read q24 in the faq. 2. please post a small slice of this raw, so i can analyze it.

What sound card are you using? I want to do the same thing with DTS laserdiscs which I would imagine would be much less trouble due to it being the same bitrate as PCM... I thinking of getting an Audigy 2 for the task. Also... what software did you use to record the stream?

I asked for the best and brightest .... and you did not disappoint ;) It worked! Many, many thanks! Ah the joys of a certain sci-fi trilogy in proper AC3 .... ahhhhhh. I wouldn't try it with the Audigy ... I think all the creative cards resample the signal and kill the AC3. You need a card that does pure digital copies of the SPDIF bitstream. Mine is a C-Media soundcard built onto the motherboard. No clue how one would go about fixing this with DTS. What seems to happens with the AC3 is that it gets a packet each fraction of a second and then nothing for a fraction of a second before the next AC3 packet. Hence you end up with a file that is rather like an Ac3 WAV with the gaps in there. It's not possible to rename it to .ac3 then author with this as the program cannot seem to read the length of the ac3 file. Also the file is about 4 times the size it should be due to all the redundant gaps in the stream. But besliced cut it to perfection! Well done!!! Best, Quilty

Thanks for the heads up on the Audigy... I was just about to get one of these, glad I saw your post first! Might look into something from M-Audio instead. What software did you use to record the stream? Also are you using the ac3 track for a dvd project? I'm just curious how it goes because coming from LD the stream will be 44.1khz rather than 48... and I'm going to face the same problem when I start doing the DTS LDs.

I'm looking to do the same thing with the AC3 tracks from a laserdisc trilogy. What software did you use? I'm borrowing a soundcard with optical and coax digital in from Turtle Beach. Apparently the sound card was OEMd by some other sound card manufacturer. I don't have the model nubmer, but TB only released 2 cards like this and I believe they are almost the same card. Right now I'm just putting the pieces together.My plan was to do an AC3 capture. Then convert the AC3 to the 6 audio waves to edit it so I can match the waves to the captured waves. I'll then take the edited waves and encode them back to AC3. The reason for these extra steps is becase I don't currently have a way to capture AC3 directly with a video capture. Any advice on tools would be great. Thanks!

Has anyoe worked on this since the initial postings? I am quite interested in this myself.

I'm keen to work on this myself but still can't figue out what soundcard to buy... anyone have any recommendations?

Any luck capturing AC3? What software? 

How goes the battle to capture AC3 files through coax SPDIF? In my case, I'm trying to timeshift DD5.1 audio and Svideo from my digital cable set top box. The video, thanks to software found here, is a snap. But the folks at Dolby are making the audio a bit more difficult. While I have purchased an M-Audio Revolution for playback, it doesn't have an SPDIF input. And it was bought with the intention of replacing the Live! Platinum with LiveDrive that I also have. I'm willing to buy a card that will do NOTHING but bit-perfect SPDIF input if there are software applications that will eventually result in an AC3 file. I've seen lists of full-featured sound cards that will apparently work, but it's the software combination that I'm really curious about. What do you folks recommend? I don't want to spend $500 on software unless I have to. Is it a matter of money, or am I still on a quest for the Holy Grail?:confused: