HDMI Audio Capture

[krassyg]

I managed to record Dodlby Digital 5.1 from my cable box using Blackmagic Intensity HDMI capture card. The file produced is a wave at 48Khz. I then used besplit to extract to an .ac3 file. The file plays fine, but it is 6 second shorter than the original video. Is there another tool that does the same thing as besplit?
If not, how can I extend the play time of the AC3 file?

Thanks in advance,
Chris

[jman98]

I am absolutely amazed that you were able to do this. I thought the whole point of HDMI was specifically to prevent EXACTLY this kind of thing.

Here's a better method. Record from your cable box to your PC via firewire. Edit the clip and demux. Then you've got the original AC3 file which you can do with as you please. Here's a link to drivers for firewire to PC recording via a cable box:
http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=403695

I have never used Besplit before, so I have no idea why there is a length difference unless maybe Besplit found some errors in your recorded file and this caused the difference in length. An audio editor might help you to stretch the length for 6 extra seconds, but it wouldn't get them back.

[Nelson37]

Have just recently started capturing DD Wave files with a Creative X-Fi card, SFAIK the besplit method is just about the only conversion method available.

6 seconds is a lot of time difference, I have been dealing with variances of 0.98 to 0.26 seconds. Up to about 0.40 seconds, I just split the difference and add it to the delay. I am pretty sure the variances are due to errors in the original transmission or conversion, I hear quite a few in the original broadcast. Short pops or audio stutters. Not in all movies, in fact this seems related to quality of original film.

Delaycut can add delay and crop for length. AC3Machine used to transcode seems to remove errors which choke authoring programs. MPG2CUT2 can correctly edit the M2V muxed with the 5.1 AC3.

Then there is the "Black GOP" problem. Apparently this is the reason most DVDs demux with a delay factor for the AC3 file, from what I read leading silence is simply removed. Crude workaround is to cut on the beginning fanfare, rather than on silent black frames.

BeSweet and others can demux to 6 wave files, apparently Hypercube Transcoder is pretty good at this. These waves could then be individually stretched, then re-encoded as AC3. For this you need a good quality encoder. If for some strange reason you would like a multichannel MPG, Hypercube does this well. Virtually no good quality free 5.1 encoders, possibly Aften but I have not spent much time with this as I just bought Vegas. However, that particular software will not play an AC-3, nor allow an unmuxed one onto the timeline, won't extract to WAV, and instead of 6 mono Wav files, the front and rear must be 2-channel stereo, left and right apparently a crapshoot.

And before some smartass says so, RTFM does not say dick about ac3 creation from wav files.

But anyway, I saw your hardware listing on the other post, could you give some more detail on your process, progs used, and source type? Does this work on all channels, including HD?