Merging eight ProRes audio streams into 5.1 for DCP conversion

[mrbliss]

I'm stuck again. I'm in the advanced mixing options and I can't work out some of the channels. Crucially, I need to know the difference between FR - L and FL. Which is front left, and why isn't there an FR channel?

Also, do I select 8 channels for an 8.1 mix? What is Front L & R Matrix, is it the same as Side L & R in audacity?

[poisondeathray]

I'm stuck again. I'm in the advanced mixing options and I can't work out some of the channels. Crucially, I need to know the difference between FR - L and FL. Which is front left, and why isn't there an FR channel?

Also, do I select 8 channels for an 8.1 mix? What is Front L & R Matrix, is it the same as Side L & R in audacity?

7.1 is 8 channels => this is what you have
8.1 is 9 channels , and not a common configuration

The naming convention was given in an earlier post FL+FR+FC+LFE+BL+BR+SL+SR . That's the order you should use

If you are using mediainfo names, the Front L (matrix) would correspond to SL , The Front R (Matrix) would correspond to SR

If you look closely at mediainfo the audio #1 is FL, audio #2 is FR, etc.... they corresond to the order given above

[poisondeathray]

I'm using VLC at the moment to save the video stream only. I'll look at the FFMpeg option afterwards. Its going to be another very late night for me!

I don't know why you're doing this ? video stream only ?

Did you want video stream without audio separately ? If so

ffmpeg -i input.mov -c:v copy -an output.mov

Otherwise you're wasting time with VLC, because ffmpeg can copy the video from the original and mux your new audio in 1 step

And if you're still using VLC for this , make sure you have it COPY the stream, not encode to some other format, or it will take a longer time, and you lose quality

[mrbliss]

Its rendfering now. I selected WAV 16bit rather than the option I was using before and the channel came up exactly as the you gave above. I think something else has gone wrong though as while I was doing that, all but one of the tracks turned grey?

[poisondeathray]

What you could do is render out a selection (highlight, say 30 seconds), to use as a test with a given set of settings, and see if it works first. Then adjust your settings, maybe select better options 24bit, etc... see if that works, then go back, adjust etc... ie do a bunch of mini tests first so you don't waste time rendering the whole thing to only find out the other program doesn't like it

[mrbliss]

I'm using VLC at the moment to save the video stream only. I'll look at the FFMpeg option afterwards. Its going to be another very late night for me!

I don't know why you're doing this ? video stream only ?

Did you want video stream without audio separately ? If so

ffmpeg -i input.mov -c:v copy -an output.mov

Otherwise you're wasting time with VLC, because ffmpeg can copy the video from the original and mux your new audio in 1 step

And if you're still using VLC for this , make sure you have it COPY the stream, not encode to some other format, or it will take a longer time, and you lose quality

Yes, I was using VLC as it can make a direct copy of the video without the audio (and put it in a different container if need be). I've done this dozens of times and its worked perfectly, but this time I ended up with another 1k file!

[mrbliss]

damm and blast I knew that grey meant some thing, sounds like just one of the surrounds was muxed.

[poisondeathray]

In the channel map, a line has to be connected from the input to the output.

If you organize the tracks in the timeline in the standard order, they will already be connected in that same order automatically. That's the reason for naming the mono tracks FL, FR, etc... when they were extracted. If you left click the name of the track in the timeline, there will be an option to "move track up" or "move track down"

[mrbliss]

What you could do is render out a selection (highlight, say 30 seconds), to use as a test with a given set of settings, and see if it works first. Then adjust your settings, maybe select better options 24bit, etc... see if that works, then go back, adjust etc... ie do a bunch of mini tests first so you don't waste time rendering the whole thing to only find out the other program doesn't like it

Is there an easy way to edit out a short clip while retaining the same audio and video settings?

[mrbliss]

From the MediaInfo, it looks like irs worked:

General
Complete name : C:\Users\Film\Documents\Audacity\k46.wav
Format : Wave
File size : 3.95 GiB
Duration : 1h 32mn
Overall bit rate mode : Constant
Overall bit rate : 6 144 Kbps
Writing application : Lavf56.1.100 (libsndfile-1.0.24)
Software : Lavf56.1.100

Audio
Format : PCM
Format settings, Endianness : Little
Format settings, Sign : Signed
Codec ID : 1
Duration : 1h 32mn
Bit rate mode : Constant
Bit rate : 6 144 Kbps
Channel(s) : 8 channels
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Stream size : 3.95 GiB (100%)

But I'm not hearing speech, is that because VLC can only play in stereo?

[poisondeathray]

VLC can play in more than stereo if you have it set up to do so

Reimport the wave into audacity to test it. You can also solo each track to test each channel

[poisondeathray]

What you could do is render out a selection (highlight, say 30 seconds), to use as a test with a given set of settings, and see if it works first. Then adjust your settings, maybe select better options 24bit, etc... see if that works, then go back, adjust etc... ie do a bunch of mini tests first so you don't waste time rendering the whole thing to only find out the other program doesn't like it

Is there an easy way to edit out a short clip while retaining the same audio and video settings?

Yes, just make a selection in audacity

e.g let's say you want from 1min 10sec to 1min 40 sec, for a 30 sec duration clip - just left click and hold and slide over that segment you want. It will only be highlighted for the 1st track, so you use edit=>select=> in all tracks (or ctrl + shift + k) , then all 8 tracks will be selected for that 30 seconds and highlighted. Then file=>export selection , and the rest is the same


Or were you actually asking about something else ? because you mentioned "video settings" ?

[mrbliss]

What you could do is render out a selection (highlight, say 30 seconds), to use as a test with a given set of settings, and see if it works first. Then adjust your settings, maybe select better options 24bit, etc... see if that works, then go back, adjust etc... ie do a bunch of mini tests first so you don't waste time rendering the whole thing to only find out the other program doesn't like it

Is there an easy way to edit out a short clip while retaining the same audio and video settings?

Yes, just make a selection in audacity

e.g let's say you want from 1min 10sec to 1min 40 sec, for a 30 sec duration clip - just left click and hold and slide over that segment you want. It will only be highlighted for the 1st track, so you use edit=>select=> in all tracks (or ctrl + shift + k) , then all 8 tracks will be selected for that 30 seconds and highlighted. Then file=>export selection , and the rest is the same


Or were you actually asking about something else ? because you mentioned "video settings" ?

Yes video settings. Ideally I want to test a small section of video & audio, so I can see that they are in sync and hear that all the sound is there. I want to keep it in exactly the same format so that I know I can set the whole film to render without having to worry if its going to work or not.

[poisondeathray]

Yes video settings. Ideally I want to test a small section of video & audio, so I can see that they are in sync and hear that all the sound is there. I want to keep it in exactly the same format so that I know I can set the whole film to render without having to worry if its going to work or not.

Yes, you can stream copy a segment with ffmpeg

-t is the duration in hh:mm:ss.ms
-ss is the start time in hh:mm:ss.ms

e.g.

Let's say you want to copy a section from 10 minutes, to 11 minutes, for a total duration of 1min

ffmpeg -i input.mov -c:v copy -c:a copy -ss 00:10:00 -t 00:01:00 output.mov

And if you have multiple streams (not single audio + single video), you chould actually use -map 0 -c copy for copy all

ffmpeg -i input.mov -map 0 -c copy -ss 00:10:00 -t 00:01:00 output.mov

But that doesn't necessarily guarentee that it's going to work. For example , what if the audio aborts at 30 minutes like in the earlier example ? But it does give you some quick & dirty feedback if something for sure doesn't work

[mrbliss]

Result! MediaInfo reports output.mov as having 8 channels. It plays ok on my PC, sound in sync etc, so I'm going to start rendering. Had problems trying to make a segment, but I'm running out of time so just need to go for it.

[CarlHetherington]

For what it's worth, you can add multiple WAV files to a DCP-o-matic project and then map each one to the appropriate place.

Use the "Add files" button to add each WAV file. Then you can select each in turn in the file list, go to the audio tab and set which DCP channel that file should go to.

If you need any help do feel free to send email to our mailing list dcpomatic@carlh.net or direct to me (main author) carl@dcpomatic.com

DCP-o-matic's inability to use the audio channels from your original Prores file is a weakness; fixing it is on the to-do list.

[mrbliss]

For what it's worth, you can add multiple WAV files to a DCP-o-matic project and then map each one to the appropriate place.

Use the "Add files" button to add each WAV file. Then you can select each in turn in the file list, go to the audio tab and set which DCP channel that file should go to.

If you need any help do feel free to send email to our mailing list dcpomatic@carlh.net or direct to me (main author) carl@dcpomatic.com

DCP-o-matic's inability to use the audio channels from your original Prores file is a weakness; fixing it is on the to-do list.

Hi Carl, nice to have you in this thread. I tried what you describe and I can't quite remember why but it didn't seem right. I think there wasn't drop down on the tracks to select left, right etc. I can't look right now as it still rendering.

I have a more pressing query now as I think I made a mistake in that our system is only 5.1 not 7.1. I actually mapped the sides (the streams in the original file were called L&R Matrix?) to the back as these last two didn't seem to be available on DCP O Matic. So 4 channels are going to 2 speakers. My concern here is that our system will refuse to play it. I thought it would just mix it internally to 5.1, but our projectionist thinks not.

Any idea if this will work or not? I'm half way through the rendering, six hours to go. I have an electrician coming to re wire my flat tomorrow morning, so only about 15 hours of rendering time left before the leccy goes off!

[mrbliss]

Bit the bullet & stopped it, but when I went back to the sound settings, it looks like I had done it correctly as it said something like "stream will be passed unaltered to DCP channel 5/6". I've unchecked 7 & 8, and it seems like it will pick up where it left off. If there's time, I'll save the 6 channel mxf and try the 8 channel version again and we can try an ingest both and see what the projector makes of it.

[mrbliss]

Its finished rendering and it looks like the sound is ok, but while focusing on that I've made a mistake with the aspect ration. The film is scope in a 16:9 frame, I scaled the input video to scope and set the DCP container to scope. The result is the video is stretched within the scope frame. Is there an easay way (without starting again) to change the aspect ratio of the MXF? I don't think this can be done by the projector/server?

[CarlHetherington]

I tried what you describe and I can't quite remember why but it didn't seem right.

I've just put a video up here which might demonstrate things more clearly.

My concern here is that our system will refuse to play it. I thought it would just mix it internally to 5.1, but our projectionist thinks not.

I'm not entirely sure what will happen there. The back surround channels might appear in your hearing impaired / visually impaired channels, if you use them.

Its finished rendering and it looks like the sound is ok, but while focusing on that I've made a mistake with the aspect ration. The film is scope in a 16:9 frame, I scaled the input video to scope and set the DCP container to scope. The result is the video is stretched within the scope frame. Is there an easay way (without starting again) to change the aspect ratio of the MXF? I don't think this can be done by the projector/server?

I'm afraid I think you have to re-make the DCP. The missing step is to crop the black from the input file so that it ends up in a Scope aspect ratio. The rest of your settings sound right. DCP-o-matic makes no attempt to remove letterboxing or pillarboxing from input files.

Do let me know you have trouble.

[mrbliss]

I tried what you describe and I can't quite remember why but it didn't seem right.

I've just put a video up here which might demonstrate things more clearly.

My concern here is that our system will refuse to play it. I thought it would just mix it internally to 5.1, but our projectionist thinks not.

I'm not entirely sure what will happen there. The back surround channels might appear in your hearing impaired / visually impaired channels, if you use them.

Its finished rendering and it looks like the sound is ok, but while focusing on that I've made a mistake with the aspect ration. The film is scope in a 16:9 frame, I scaled the input video to scope and set the DCP container to scope. The result is the video is stretched within the scope frame. Is there an easay way (without starting again) to change the aspect ratio of the MXF? I don't think this can be done by the projector/server?

I'm afraid I think you have to re-make the DCP. The missing step is to crop the black from the input file so that it ends up in a Scope aspect ratio. The rest of your settings sound right. DCP-o-matic makes no attempt to remove letterboxing or pillarboxing from input files.

Do let me know you have trouble.

Thanks Carl, the video makes sense of it now, all I needed to do was unselect all the audio on the video and then select each audio file in turn and map it. That really straight forward, I think I was to tired & frustrated to think clearly about it.

And after all that, we can't change the aspect ratio of the DCP with the projector, so we're having to use a DVD as a back up. But I'll know what to do next time.

Does DCP O Matic only handle up to 5.1 then?

Thanks for this great software and your help with this problem. Thanks also to poisondeathray and the others in this thread.

[CarlHetherington]

Does DCP O Matic only handle up to 5.1 then?

No, DCP-o-matic will do 7.1. You can choose how many audio channels the DCP has in the "DCP" tab. It defaults to 6 for 5.1

[mrbliss]

Does DCP O Matic only handle up to 5.1 then?

No, DCP-o-matic will do 7.1. You can choose how many audio channels the DCP has in the "DCP" tab. It defaults to 6 for 5.1

Ah, missed that one!

[mrbliss]

[QUOTE=CarlHetherington;2341041]

My concern here is that our system will refuse to play it. I thought it would just mix it internally to 5.1, but our projectionist thinks not.

I'm not entirely sure what will happen there. The back surround channels might appear in your hearing impaired / visually impaired channels, if you use them.

What is the usual practice when mixing down from 7.1 to 5.1 sound? Presumably two of the channels need to be mixed into two others, but which ones?

[El Heggunte]

^ (Side Channels + Rear Channels) / 2

BL+BR (5+6), SL+SR (7+8)

I think PDR meant BL+SL (5+7) && BR+SR (6+8)

[poisondeathray]

What is the usual practice when mixing down from 7.1 to 5.1 sound? Presumably two of the channels need to be mixed into two others, but which ones?

Usual practice is to mix BL+BR (5+6), SL+SR (7+8)

FL,FR,C,LFE remain untouched

[mrbliss]

^ (Side Channels + Rear Channels) / 2

BL+BR (5+6), SL+SR (7+8)

I think PDR meant BL+SL (5+7) && BR+SR (6+8)

Thanks, I thought that was probably how it was done, but just wanted to check.

[poisondeathray]

Yes sorry, Left and left, Right and right .... Right ?