Audio question 2.0 vs 5.1

billmich

Member
I was playing around recently I noticed a few things about stereo vs Multi channel on VRD and have a couple of questions.
I will preface by noting that I understand that if the audio line is yellow= 5.1 and if it is blue it is 2.0.

1) If I have a 5.1 audio source and I use the audio adjustment slide to increase or decrease the volume of the subsequent saved file, it always is saved as 2.0. Is this a hard and fast rule, or is there a work around so I can keep it as 5.1 audio?

more importantly: 2) If I have 2 files, and 1st is 2.0 and the 2nd is 5.1 and I use the joiner function, the ENTIRETY of the new saved file appears to be 2.0. Why cant the audio be 2.0 for the 1st segment and 5.1 for the rest, or have the entire thing be 5.1 (with the 1st segment only outputting the left/right channels and the other 3 are just dead?

Is there a setting or work around this particular conundrum?

Any assistance would be greatly appreciated
 

jmc

Well-known member
I was playing around recently I noticed a few things about stereo vs Multi channel on VRD and have a couple of questions.
I will preface by noting that I understand that if the audio line is yellow= 5.1 and if it is blue it is 2.0.

1) If I have a 5.1 audio source and I use the audio adjustment slide to increase or decrease the volume of the subsequent saved file, it always is saved as 2.0. Is this a hard and fast rule, or is there a work around so I can keep it as 5.1 audio?

more importantly: 2) If I have 2 files, and 1st is 2.0 and the 2nd is 5.1 and I use the joiner function, the ENTIRETY of the new saved file appears to be 2.0. Why cant the audio be 2.0 for the 1st segment and 5.1 for the rest, or have the entire thing be 5.1 (with the 1st segment only outputting the left/right channels and the other 3 are just dead?
You should go into Advanced Audio settings and "set" the channels you want.

If AC3 and changing the audio level then it will always be recoded to a non AC3 audio.

I believe VRD goes by the FIRST audio steam it finds.
You would need to process the 2ch to 5.1 ch separately then "join".

In testing I changed a 6ch AC3.mpg to 6ch PCM.mpg.

OUCH, not the white noise I have run into using the Automatic setting before.
You can sorta understand the words but LOTS of static.

jmc
 

Danr

Administrator
Staff member
In testing I changed a 6ch AC3.mpg to 6ch PCM.mpg. OUCH, not the white noise I have run into using the Automatic setting before.
Post the Tools>Show Program Info of the source file here. We need to check this out.
 

jmc

Well-known member
Post the Tools>Show Program Info of the source file here. We need to check this out.
EDIT... Oh, it seems to be a VLC problem. VRD and MPClassic do not have static.

VRD5 748
-----------------Source File 5.1AC3.MPG-----------------------------------------------------
File: Name : R:\5-1BB-5Min.mpg
Size : 0.161 GB
Duration : 00:05:00.14
Mux type : PS - MPEG2
Video: Encoding : MPEG2
VideoStreamID : xE0
Frame rate : 29.97 fps
Encoding size : 720 x 480
Aspect ratio : 16:9
Header bit rate : 7.500 Mbps
VBV buffer : 224 KBytes
Profile : Main@Main
Progressive : Prog or Int
Chroma : 4:2:0
Bit rate : 3.746 Mbps
Captioning : None found
Field order : Progressive
Audio Stream: 1 (Primary) Codec : AC3
Channels : 5.1
Sub stream id : x80
Bit rate : 384 Kbps
Sampling rate : 48000
Sample size : 16 bits

--------------Here is the Audio info of 5.1PCM.MPG Created--------------------------------------------------------------------------

Audio Stream: 1 (Primary)
Codec LPCM Channels 6.0
PID xA0 PES Stream Id xBD
Bit rate 4608 Kbps Sampling rate 48000
Sample size 16 bits
--------------------------------------------------------------

Thanks,
jmc
 
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Dan203

Senior Developer
Staff member
VLC does not support 6ch PCM. I ran into this during testing when I first started making all the big audio changes a couple years ago. As far as I can tell their PCM in .mpg file support only works for files that comply with the DVD standard, which is 2ch and either 16 or 20 bit.
 

billmich

Member
So what were the things I needed to do about my issues?

Should I be combining instead of joining?
 
Last edited:

Dan203

Senior Developer
Staff member
We do not have a 5.1 AC3 encoder in VideoReDo. So if you adjust the audio volume at all the output will be 2.0.

I'm not 100% sure about the joiner. It should be able to retain a mix of 2.0 and 5.1, but I'd need to look at the logic to be sure. Although the properties of the output file will always list the audio of the first file in the list, so you'd have to open the file back up in VRD and check the yellow/blue line to see if the 5.1 was actually retained.
 

billmich

Member
Thank you for answering about #1

as for #2 i have checked in the past, and it was a blue line throughout - I checked in segments that were originally yellow (5.1) - if you could get back to me on this , It would be more appreciated. Is there any setting in advanced audio menu that I should be looking at to ensure that the 2.0 stays 2.0 and the 5.1 stays 5.1?
 

jmc

Well-known member
how is THAT done?
Ok, you would
Save>Profile Options, Audio(click on "Advanced" -far right)
Click on "Edit" and change the areas needed.

Now the options available will change according to the type of
audio you are dealing with...

"MPEG Layer 2" will NOT give you a 5.1ch option.

LPCM/WAV will give you 5.1.

AAC will be available with something like .MP4s and have 5.1 available

You can create "Elementary Streams" and change the audio streams in the video.
(Elementary Stream Muxer)
(Audacity will also convert audio types from one to another)


Good luck,
jmc
 
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billmich

Member
Ok, you would
Save>Profile Options, Audio(click on "Advanced" -far right)
Click on "Edit" and change the areas needed.

Now the options available will change according to the type of
audio you are dealing with...

"MPEG Layer 2" will NOT give you a 5.1ch option.

LPCM/WAV will give you 5.1.

AAC will be available with something like .MP4s and have 5.1 available

You can create "Elementary Streams" and change the audio streams in the video.
(Elementary Stream Muxer)
(Audacity will also convert audio types from one to another)


Good luck,
jmc
Some good stuff to play around with.
Will i be able to join 1 segment with AAC/LPCM with another segment that is MPEG2?

I did notice that MPEG 2 is only (automatic, 2.0, 1.0)
:(
 

Dan203

Senior Developer
Staff member
If you combine file with different audio codecs then the audio will always be recoded. And in most cases it will use 2.0 MP2 or AAC. You can force 5.1 AAC for H.264 output, but if the source is 2.0 it will simply fill the missing channels with silence. It won't do any sort of virtual surround sound.
 

billmich

Member
If you combine file with different audio codecs then the audio will always be recoded. And in most cases it will use 2.0 MP2 or AAC. You can force 5.1 AAC for H.264 output, but if the source is 2.0 it will simply fill the missing channels with silence. It won't do any sort of virtual surround sound.
Dan, that is EXACTLY what I want it to do.
So if I have file 1 that is 2.0 and file 2 that is 5.1, do I "join them" and use this AAC 5.1 "force" in order to get 5.1 on everything?

I have never really played around with the "combine" feature, I have always used 'Join'

My most common scenario is if I have a preempted game and the 1st segment is via the watch ESPN app which I can only get via 2.0 audio.
I am more than happy with the 1st 3 minuted being 2.0(actually 5.1 but only the l/r channels active) and the rest being in FULL 5.1
 

Dan203

Senior Developer
Staff member
Combine is only used for sequential files that were split from one source file, like VOB files on a DVD. It wont work for most things. So join is what you want.

Yes if you force the output audio to AAC Surround then it will recode the 2.0 files in the joiner to 5.1 by filling the missing channels with silence. This is the only way to get 5.1 sound if you're saving AAC to MP4 as MP4 uses a common header for all AAC audio and does not allow mid stream switches like AC3 does.
 

billmich

Member
Combine is only used for sequential files that were split from one source file, like VOB files on a DVD. It wont work for most things. So join is what you want.

Yes if you force the output audio to AAC Surround then it will recode the 2.0 files in the joiner to 5.1 by filling the missing channels with silence. This is the only way to get 5.1 sound if you're saving AAC to MP4 as MP4 uses a common header for all AAC audio and does not allow mid stream switches like AC3 does.
I would be saving in the H.264 format
 

Dan203

Senior Developer
Staff member
H.264 is a video codec not a format. The format is the contain the audio and video is store in, for H.264 video that can be TS, M2TS, WTV, MP4 or MKV. MP4 and MKV use a special method for storing AAC audio where they strip the headers from the individual audio frams and store just a single header at the container level. This reduces the size of the file, but makes it impossible to have a stream where the channels change mid stream. So if you're saving as MP4 or MKV then you need to force the audio to 5.1 rather then using automatic.
 

billmich

Member
H.264 is a video codec not a format. The format is the contain the audio and video is store in, for H.264 video that can be TS, M2TS, WTV, MP4 or MKV. MP4 and MKV use a special method for storing AAC audio where they strip the headers from the individual audio frams and store just a single header at the container level. This reduces the size of the file, but makes it impossible to have a stream where the channels change mid stream. So if you're saving as MP4 or MKV then you need to force the audio to 5.1 rather then using automatic.
Can I force 5.1 if I am using .M2TS?
 

billmich

Member
We do not have a 5.1 AC3 encoder in VideoReDo. So if you adjust the audio volume at all the output will be 2.0.

I'm not 100% sure about the joiner. It should be able to retain a mix of 2.0 and 5.1, but I'd need to look at the logic to be sure. Although the properties of the output file will always list the audio of the first file in the list, so you'd have to open the file back up in VRD and check the yellow/blue line to see if the 5.1 was actually retained.
I am assuming version 6 does have that type of encoder because I played around yesterday and increased audio in a segment and it stayed at 5.1 audio… This is a nice feature ad
 
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