How to capture AC3?

[W_Eagle]

My cable TV and satellite TV receivers have now AC3 output, 2 channels and sometimes 5.1 channels, on optical SPDIF output. I plan to purchase a sound card with optical SPDIF input. So far I captured movies as avi with wave audio. I prefer capture the AC3 and, if possible, use the original AC3 files up to the DVD authoring. However, if it's possible to capture the AC3 files, convert it to wav and than to AC3 again, it will do.

Only, how would I capture AC3 data, preferably as AC3 files?

[Nelson37]

Do a search for my previous post.

Post back with any additional questions.

[W_Eagle]

Do a search for my previous post.

Post back with any additional questions.

Thanks.
I searched the forum prior to posting my question, however I didn't see any applicable info.

[Baldrick]

https://forum.videohelp.com/topic339168.html

[W_Eagle]

https://forum.videohelp.com/topic339168.html

Thanks.
I read this post while searching, however, it is unclear to me from that post how to capture AC3.

[W_Eagle]

To make my question clearer.
What software (or software/hardware combination) will capture avi files with AC3 audio?
If that's not possible, what software will capture avi files, decoding on the fly AC3 audio into wave?

[Nelson37]

Search some more.

24-bit, Bit-Accurate sound card with SPDIF-in. M-audio24/96 card, certain Audigy cards, one mentioned from Terratec. Only one I can verify is the Creative X-Fi.

Virtualdub reported to cap AC-3 stream with video. I do real-time MPG with ATI MMC with real-time WAV recording of the streaming AC-3, so cannot verify this. Several softwares verified to capture the 24-bit stream accurately, others failed. Creative app works, Goldwave only other I can verify.

You need the BeSplit trick to convert the stream to standard AC-3.

[W_Eagle]

Thanks.
Will Goldwave capture both audio and video?
Will it capture the AC3 stream as AC3, or as wav?

[Nelson37]

Goldwave is audio only.

Audio MUST be captured as 24-bit, 48khz stereo WAV. No processing or filtering of any kind. If the recording is not "bit-accurate", it will not produce an AC-3 file. Most audio cards with SPDIF-in apparently can NOT do this.

You end up with a WAV file, technically a "DDWAV", or streaming AC-3 file. It is possible but not recommended to run this file directly into a SPDIF input and get AC-3 playback. Most software will play this back as pulsing static.

You run this file thru a BeSplit DDWAV conversion and end up with a true AC-3, as broadcast. 5.1 or 2.0 or whatever it originally was.

The process is somewhat complicated, but once you get it down it is easy to implement. It's all a matter of having the right soundcard, tried two other "24-bit" cards which did not work.

Vdub is the only way I have seen mentioned to do both at the same time, meaning audio and video, with one program. The audio must still be processed with BeSplit.

[W_Eagle]

Thank you, Nelson.

So, with bit accurate 24-bit sound card and VirtualDub I can capture both audio and video. I assume it will be into 1 avi file. Than I'll need probably to extract the DDWAV file fro the avi file (or it may not be necessary?). Than I'll have to process the audio file with BeSplit and get the original DD AC3 file.

Is the above correct?

Another question.

Between capturing the wave audio coming from the analog audio output of the receiver and capturing the original AC3 stream – will there be much quality difference?

[Nelson37]

I don't use the Vdub way but your method seems right. Vdub can be set to capture to seperate files, under striping.

An analog capture gives you at best a Stereo Prologic downsampled analog file. The digital capture yields a much-better true 5.1 (if broadcast that way) sound file.

How much better? Well, that's the question you must answer. In order to answer it, you must obtain the hardware and perfect the capture method. Once you've already done that, the question becomes Why Not?

Editing is much more fun, you may encounter time -delay or -compression issues, and there is a 2-Gb limit on the file size, which makes King Kong about 20 minutes too long. But, if you have the surround speakers, this is what you bought them for.