NicAC3Source Decodes Valid AC3 to (Largely) Silent WAV

[CarlEdman]

I have been using NicAC3Source to decode AC3 tracks from my DVDs to WAV (and ultimately AAC through neroaacenc) for some time without problem.

Recently, I've run across problems with AC3 from broadcast HD streams. I use dgindex to demux the AC3 stream which appears to work well; at least the resulting AC3 stream plays perfectly well in VLC.

However, the wav output from NICAC3Source, while well-formed and correct in length, consists out of a few minutes or so of properly decoded audio followed by silence for the remainder of the duration. This problem occurs with or without DRC or channel mixing.

Has anybody encountered this problem before or otherwise have a suggestion? I'm unsure about posting a clip because (a) it would be large and (b) there may be copyright considerations.

:thanks:

[b66pak]

first try to fix the .ac3 file with delay-cut and post the log....

http://forum.doom9.org/showthread.php?p=1246699#post1246699
_

[CarlEdman]

Thanks for the suggestion, b66pak.
:thanks:

I did try using the delaycut 1.2.1.2 "fix" function on the AC3 files, but that does not seem to have made any difference. The AC3 track still plays fine, while the NicAC3Source converted WAV file turns silent after a few minutes and for the remainder of the duration.

The attached log file offers a potential clue: The "basic parameter" change at frame 2501 seems to coincide with the switch to silence in the resulting WAV file.

Is there anything that can be done to fix this?

[tebasuna51]

Seems you have a invalid ac3 file with 2.0 and 5.1, very common in TV captures, you must split (Delaycut) the file at frame 2501 and decode both streams.

[CarlEdman]

Thanks, tebasuna51. That is what I feared after seeing the log file. Probably it is 2.0ch for the "previously on" cuts at the beginning and then 5.1ch for the remainder of the actual show.

Manually splitting is certainly doable, but may be too much trouble for automatic archiving of captured broadcasts. I take it there is no automatic way for NicAC3Source to save the entire thing as maximum-channel wav?

[tebasuna51]

AviSynth need know, before star decoding, the number of total samples to obtain, and is not possible if there are different kind of frames.

Use command line decoder azid (http://www.doom9.org/Soft21/Audio/azid-1.9.zip) with this syntax:

azid -d3/2 -L0 -l1 -ol,r,c,lfe,sl,sr mixed_input.ac3 output.wav

[CarlEdman]

Thanks again, tebasuna51. I'll try that!