Adding Delay to EAC3 Track

[alleycat]

Hi All,

Having a bit of a nightmare. 

I've got an EAC3 track from a HDTV recording and it needs a few seconds adding to the start of it to make it in sync with the video. I've successfully managed to do this with eac3to.exe using "eac3to.exe input.eac3 output.eac3 +xxxms". The problem I've just discovered is on playback those extra seconds have a very loud buzzing sound on all channels. 

I can convert to the EAC3 to wavs, either add the silence to the original version or silence out the buzz in audacity fine, but I can't find any way of converting it back to EAC3, eac3to.exe says the conversion of wav to eac3 cannot be done. 

I could convert the wavs to DTSHD but I am very tight on disc space for this project and DTS HD is massive compared to eac3. 

Anyone have any suggestions? 

Thanks

[Stamper]

Audacity can re-export as AC3, all you have to do is put in audacity the ac3 plugin.

[alleycat]

Audacity can re-export as AC3, all you have to do is put in audacity the ac3 plugin.

I don't think it can export as EAC3 though only AC3, and from what I understand that will result in a quality drop?

[alleycat]

Ok I figured it out using FFMPEG. The code is:

ffmpeg -i input.eac3 -af "volume=enable='between(t,0,06.141)':volume=0" -b:a 640k output.eac3

This produces an identical eac3 file that has 0 to 06.141 seconds muted so it removes the buzz. I guess I could have used this to add the delay instead of eac3to.exe and would perhaps have never had the buzz in the first place but at least it's fixed.

[deleted user]

The best would still be to find a method to do this without reencoding, as lossy to lossy encoding always results in quality loss and should be avoided.

Have you tried delaycut? Also, you could try creating a silent eac3 file of the correct length and then losslessly joining it with the file you have.

[alleycat]

Delaycut adds a buzz the same way as eac3to did unfortunately. I was able to create silence but was struggling to find something that could merge the two files together as EAC3.

The only thing is, doing what I did ffmpeg only took a few seconds, so I wonder is it actually re encoding it all? I don't have a slow computer but I imagine re-encoding the entire file would take more than a few seconds?

[schorman]

If you've created a silent eac3 file, you can just use something like "simple file joiner" to combine the two eac3 files. there's no file header on eac3 or ac3 tracks that might prevent simple file concatenation from working.

[alleycat]

If you've created a silent eac3 file, you can just use something like "simple file joiner" to combine the two eac3 files.  there's no file header on eac3 or ac3 tracks that might prevent simple file concatenation from working.

Schorman - give yourself a gold star! Thanks I didn't even think about something like a simple file joiner, I thought I would need some kind of audio editing tool. 

Created the silence using:

ffmpeg -f lavfi -i "anullsrc=channel_layout="5.1(side)"ample_rate=48000" -to 03.264 -b:a 640k "silence.eac3"

Then joined and it works fine.