NicAUDIO bug report: problem with certain ac3 streams

[mroz]

The ReadMe for NicAudio.dll asks to report bugs to Nic via these forums, so I hope this is the right place to post.

I'm having trouble decoding a particular ac3 stream. There's a sample at http://www.mediafire.com/?8e2q11zffmi

So far the problem seems local to my system as at least one person has processed this file using Megui which makes internal use of NicAC3source.

On my system I've tried two AviSynth builds, 'AviSynth 2.57 tsp MT version 5, build:Mar 1 2007 [21:27:12]' & 'AviSynth
2.57, build:Dec 31 2006 [13:16:28]'. Both give the same results.

I've also tried with each of the above, two versions of NicAudio.dll. One dated 20/7/06 & the other, the latest 1.7 from 13/8/07.

The sample is 90s long with 26s of silence at the start. With the 20/7/06 build, it plays to 10s then terminates. With the 13/8/07 build, it plays all the way through, but there is no audible output.

Belight is happy to transcode the ac3 stream. If I transcode back to 2ch ac3 & try to decode that file via NicAC3Source, it works correctly with either version of the plugin.

So, to recap, I seem to be seeing some longstanding problem interaction between the plugin & certain ac3 streams only, however it isn't necessarily easily repeatable by others.

I'd appreciate third party testing of the plugin against the sample stream & also any comments on what might be happening.

Cheers.

[tebasuna51]

So, to recap, I seem to be seeing some longstanding problem interaction between the plugin & certain ac3 streams only, however it isn't necessarily easily repeatable by others.

The problem is:
- The first 267 frames from your sample are stereo with Dolby Surround Mode: 0 (not indicated)

- The rest are stereo with Dolby Surround Mode: 2 (Dolby Surround encoded)

NicAudio fix with the first frame the basic parameters:
Samplerate, bitrate, channels and Dolby Surround Mode.

If any frame don't match fill the frame with silence, then you obtain all the file silenced.

Of course NicAudio must be corrected because Dolby Surround Mode is not so important to reject the frames.

[mroz]

Thanks a lot for a comprehensive explanation so quickly :)

May I ask what you used to analyse the sample?

I hope we can see this fixed.

I'm also puzzled now as to how someone else was unable to see this problem with the sample concerned - unless either 1.7 isn't the most recent or an intermediate version didn't suffer with this issue and happened to be what they used.

[tebasuna51]

May I ask what you used to analyse the sample?

I hope we can see this fixed.

I'm also puzzled now as to how someone else was unable to see this problem with the sample concerned - unless either 1.7 isn't the most recent or an intermediate version didn't suffer with this issue and happened to be what they used.

I detect a similar problem with streams from TV capture: movie 5.1, commercials 2.0, and cutting by video reference always rest some 2.0 frame.

With a frame not compliant old NicAudio abort the decode, like you say with the 20/7/06 build. By my suggestion Nic change the abort for insert silenced frames.

When an ac3 stream was encoded completely (or transcode back like you say) this problem can't occur because the basic parameters are constant. The problem exists when different streams are added without reencoding.

This problem may appear also using DelayCut to insert a delay to a stream Dolby Surround Encoded, the first fames inserted to compensate the delay aren't Dolby Surround Encoded.