Change audio at beginning

Winnewup

Member
Hello,

I have a transport stream recorded from sat-tv. The movie I would like to cut out has at the beginning AC3 audio with 2 channels (few frames). The movie itself has audio AC3 5.1. If I cut out the movie with VRD6 the result is a file marked as AC3 2Ch (VRD6, VLC). If I play the movie on tv (audio is played through an audio system), audio changes after 1 second to AC3 5.1, like the recorded file. So far … so good.
VRD6 supports recoding audio to AC3 5.1 if I understood it right. Is there a chance to convert the beginning of the file to AC3 5.1 without loosing quality of the original audio that is already AC3 5.1 in most of the movie?
I tried to change the output profile to the parameters of AC3 5.1 and it seems to work but it displays that audio will be recoded. If I have a look at the CPU usage it seems to be recoded the entire file. The output file is displayed as AC3 5.1 (VRD6, VLC, audio system) and the volume is slightly higher (not too bad).
But how does the recoding work? Does the decoder recognize that a part is already in AC3 5.1 ("smart recoding")? Or is there a complete recoding only from left and right channel to 5.1? I am not very familiar with audio and do not want to make the movie any worse.
 

tonys

Member
I think this is a problem that I have encountered before. Converting a cut file from ts to mkv picks up the ac3 audio setting from the beginning of the ts file - in this case 2 channel. The way to get round this is to cut the file and save it in ts format, then reload the new (cut) file and convert to mkv. It will then pick up the 5.1. format. A bit tedious but it works.....

Tony
 

Danr

Administrator
Staff member
If you tell VRD to recode the audio to 5.1 it will recode the entire audio to 5.1, but for the audio frames that are already 5.1 it won't convert them to 2.0 first. As long as you use a reasonable bit rate for the audio, I doubt you'll be able to tell the difference between the original audio and the recoded audio.
 

Winnewup

Member
Hello Dan,
that's nice to hear. So with VRD6 the advertising breaks can be cut better (if film is 5.1), because there is often an inappropriate audio change there. That was a real problem with VRD5. Some playback devices do not always work properly with cut scenes and short audio changes at the cutting point.

In the meantime, I also switched completely to VRD6. Now (build 812a) it seems to be a really good product with very few bugs left. At the moment I don't have one.
Good work (y)

Frank
 
Last edited:
Top Bottom