AC3 sound playing way too fast in DVDit 2.5 PE

[Glorfindel]

I've tried authoring my first DVD-R with AC3 audio, using the encoder built into DVDit 2.5 PE. I exported the audio from Premiere as a 48KHz mono WAV and all seemed fine - but when I played the newly-burned disc back, the audio was running much faster than normal speed (the video was fine).

Any suggestions? I know I should have emulated the disc properly before burning it, but it was only really a test!

Also, anyone know why the highest AC3 bitrate that DVDit would allow me to use was 256k? The list of possible selections went up to 443, but everything above 256 was greyed-out.

[bugster]

I would hazard a guess that the fact that your source file was mono is the problem. It wouldn't be playing it at approx double speed would it?

As for your second question, another guess but as it only handles 2-channel Ac3, the higher bitrates are probably not required and are only really useful for 5.1 or higher number of channels. As to why they are shown but greyed out, I have no idea!

[Glorfindel]

I would hazard a guess that the fact that your source file was mono is the problem. It wouldn't be playing it at approx double speed would it?

Spot-on! Could you give a quick explanation of why it's doing it?

[bugster]

I would hazard a guess that the fact that your source file was mono is the problem. It wouldn't be playing it at approx double speed would it?

Spot-on! Could you give a quick explanation of why it's doing it?

As I said, it only an educated guess but think like this.

DVDit expects two channel WAV input in order to produce two channel AC3 output. You give it single channel and it obviously doesn't check the header properly and assumes it is stereo (it probably only checks the sample rate info and not the channel count). So it takes the 1st packet of data and encodes it to the left channel. It then takes the second packet of data and encodes it to the right channel, and so on throughout the rest of the file. Result is a file half as long as the original, played at twice the speed, but in (pseudo) Stereo.

Again, this is only conjecture and I have no solid evidence other than what you have described but it does seem to make a certain amount of sense!

[monoxide77]

assuming that you set DVDit to encode to mono:

there might be a problem if your WAV (or source audio file) is in stereo. you might want to use CoolEdit or a similar audio editing tool and convert the file to mono before giving it to DVDit. or it could be the other way around. if the source is mono and you're trying to make it stereo AC3, convert your mono WAV to a fake stereo outside of DVDit first.

[Glorfindel]

My source files are supposed to be mono - they are captured from old mono VHS recordings - but my capture card forces all audio to stereo (it won't allow true single-channel mono audio recording).

Hence I end up with stereo WAVs whose right channel is empty, so I simply use "Duplicate Left Channel" in Premiere to mono them up.

I chose mono export from Premiere as I reasoned I might as well save the space on the DVD. However, for some reason DVDit wouldn't let me select the 1/0 option for AC3 encoding - or rather, it did, but the disc build failed with an error relating to the audio format. When I changed it to 2/0, everything was fine (apart from the speed, of course!)