Audio Output "Copy" AC3 5.1 -> AC3 2.0 Stereo

[douche]

Hi Jan,

I have a bugreport for AVIdemuxer.

i use win10 and AVIdemuxer 2.6.18.

The problem is already known but not in this forum.
http://www.vdr-portal.de/board16-video-disk-recorder/board7-dolby-ac3-digital/125679-avidemux-markiert-ac3-kan%C3%A4le-verkehrt-gel%C3%B6st/

I also noticed this AC3 5.1 to 2.0 problem too.
This strange behaviour was already discussed  2 years earlier.
(The two screeshots are taken from this forum.) look@ Track4

ItÃ,´s pretty funny bug, because i chose Audio Output  "copy".

What are we doing wrong?

bye bye

P.S.
Handbrake 1.0.2 also shows me AC3 2.0 ch instead of  5.1

[Jan Gruuthuse]

Try: cut lead-in up to where ac3 5.1 should start.
don't use Mark [A ]! Go to time index where 5.1 starts. Mark with [ B]. cut marked lead-in (ctrl + x)
Mark where video should end with [ B] and save to new video. Check if the newly saved video plays 5.1 and says 5.1.

[douche]

Try: cut lead-in up to where ac3 5.1 should start.
don't use Mark [A ]! Go to time index where 5.1 starts. Mark with [ B]. cut marked lead-in (ctrl + x)
Mark where video should end with [ B] and save to new video. Check if the newly saved video plays 5.1 and says 5.1.

Well done Jan!

donÃ,´t use Mark A
thatÃ,´s the solution 


*edit*
now it works as it should - thanks a lot 

[eumagga0x2a]

Mark with [ B]. cut marked lead-in (ctrl + x)

Just a small remark: "cut" (Ctrl+X) means "copy the selection to internal clipboard and delete the source". While this doesn't really matter here, a simple "delete" (Del) would have been enough.

By the way, applying this workaround may trigger a bug in Avidemux leading to the first keyframe after the deleted part being lost.

[Jan Gruuthuse]

You would like to find the sweet spot: where does the audio track switches from AC3 2.0 to AC3 5.1. Probably this is a couple of key frames before the new program starts.
As for now I've not come across or noticed a 1st key frame dropped from DVB-S/S2 streams from FTA (UK) or (D) using the method.
PS.: Did you developers not put in some logic to have that 1st key frame within the selection? Could be: my recollection is wrong.

[douche]

fyi

i retried it with setting  Mark A and B just for fun.
-> it works now, too!

This AC3 Stereo instead of 6ch problem was caused by MY wrong cutting points.
It was one keyframe earlier than it should be.
Pretty tricky to recognize but reproducible behaviour.

To recognize this easily,  i use media player classic 1.7.10 now.
https://mpc-hc.org/

Hot key shift + f10


ThatÃ,´s how it should look like

[eumagga0x2a]

As for now I've not come across or noticed a 1st key frame dropped from DVB-S/S2 streams from FTA (UK) or (D) using the method.

You are right, the method works fine, I could not reproduce the issue with a current build anymore (in assumption that attributing the issue to these steps was ever correct).