Some questions about DDWAV format and S/PDIF

[Perro Grande]

I have a question or two about the ddwav format.

When I convert an AC3 file to a ddwav file using BeSplit, the resulting file (when loaded into CoolEdit, or another WAV editor) looks exactly like what comes off a raw S/PDIF line. I describe the resulting file as "bursts" of data, evenly spaced.

As I mentioned, it looks almost exactly like what I get if I just do raw capture (non-audio data setting) from my S/PDIF input on my sound card. Is this essentially the same thing? Raw AC3 data with a WAV wrapper?

I'm experimenting capturing raw AC3 from the S/PDIF line and trying to get it into an AC3 file suitable for use on a DVD. I thought that I could capture it and have BeSplit treat it as a ddwav to get my AC3. This has not worked...


Second question about ddwav. When I convert an AC3 file to ddwav format using BeSweet, I get the file like I mentioned above. When I try to use BeSplit (using the -ddwav -fix option as described in the examples file) I get an AC3 file. While I thought it would and should return the same file that I started with, I get a VERY short (5-10 seconds) AC3 file that is completely silent. (The same thing happens when trying to convert one of my s/pdif captures.) It appears to bail out of the transcoding very quickly -- but returns no error.

ie:

AC3(original) -> DDWAV -> AC3(new)

does not result in the new AC3 being the same as the original. I get a short silent AC3 file.

also:

S/PDIF(raw capture) -> Saved as WAV -> AC3 (via BeSplit)

also produces a short, silent AC3 file.


Thus far, I believe I have only tried this with 2 channel AC3s. Is this the issue? Does the DDWAV format and the conversion utility in BeSplit assume that it is dealing with a 5.1 ddwav?

Thanks!

[Perro Grande]

Thanks, Kempfand, I'll give that a try.

I'll also try some different versions of BeSweet to make the ddwav file for experimentation. The current version I'm using is 1.5 Beta 23 -- I'll try an older non-beta build just for kicks...

[Perro Grande]

A followup:

Reverting back to an older build of BeSweet 1.4, I can now go from:

Ripped AC3 -> ddwav with BeSweet, and back to AC3 with BeSplit (although somewhere along the line, it dropped to 44.1 KHz sample rate.)

The log showed one E7 CRC error, and the file has a "pop" at the beginning of it. Otherwise, it played just fine. Apparently, there is something up with the ddwav feature in build 1.5 of BeSweet, or that it is doing something newer than BeSplit can handle...

I tried one of my "captured" ddwav files ("recorded" via SPDIF). I converted it to an AC3 using BeSplit. I logged the results -- nothing of interest.

The resulting AC3 would not play. I then used BeSweet to go from AC3 to AC3 and looked at the log -- which was jammed full of E7 CRC errors... -fix produced the same messages, and a non-working AC3 file.

[Perro Grande]

On the SPDIF recording, I have a bona-fide AC3 source connected to my sound card via its SPDIF input.

I have the card set to expect "non-audio" data -- that is, it is not expecting PCM.

I then record it with any of a variety of wav recorders.

The resulting file "looks" a lot like a DDWAV file from BeSweet, but BeSplit doesn't seem to know exactly what to do with it. I suspect it has something to do with formatting of the wav file, or perhaps timing... Don't know -- but I'm working on it!