I recently made a DCP with a 5.1 audio mix. It was played in a theater that was set up for 7.1 surround. While the movie was playing we could not hear any sound coming from the rear speakers. After the screening I inquired with the projectionists and technicians. They informed me that with a 7.1 audio system, when you feed it 5.1 audio the surround channels only play from the side speakers. To get sound in the rear speakers we would need a 7.1 audio mix. I have some questions regarding this.
1. Is this true for all 7.1 theaters?
2. If I were to artificially make a DCP with 7.1 audio (using the 12.1 audio option in DCP-o-Matic) by either (a) placing the 5.1 surround audio tracks only in the back surround channels (and leaving side surround channels empty) or (b) placing the 5.1 surround audio tracks in both the side surround and back surround channels, would that work okay? Would either option be better than the other?
3. If I have a DCP with a 7.1 audio mix using the a or b options above, what happens when it is played on a 5.1 system?
Thanks for the insight.
5.1 vs 7.1 surround
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Carsten
- Posts: 2804
- Joined: Tue Apr 15, 2014 9:11 pm
- Location: Germany
Re: 5.1 vs 7.1 surround
If this theater is not able to switch their sound system between 5.1 and 7.1, their installer did a bad job, and the cinema operator did a bad job in educating their staff. Every 7.1 cinema that has been set up properly allows to switch between 5.1 and 7.1 - because the majority of releases is still 5.1, having a 7.1-only config would be stupid.
The common cinema audio processors have switches/cue options to change their channel assignments between 5.1 and 7.1. Typically, for 5.1, the side surrounds get copied to the back surrounds, and all surrounds are slightly reduced in level to get the same surround balance as in 5.1 only systems.
All cinema processors are 5.1 initially. 7.1 then is an option to setup, and once configured, there are means to switch between the standard 5.1 and the extra 7.1 config.
As for commercial movie releases, the majority is in 5.1. When there is a 7.1 version available, then a 5.1 version is made available as well.
E.g. for an international movie, we usually receive an OV version in english, and e.g. a 5.1-VF in german and a 7.1-VF in german.
Movie trailers come in 5.1 only (with some very few exceptions).
I f you play a 7.1 DCP on a 5.1 system, the back surround channels will not be audible. I don't know any cinema processor that allows to mix rear surrounds to side surrounds. Wouldn't make sense anyway, since, if a processor would have access to rear surround channels, it would necessarily be a 7.1 capable processor. And so it wouldn't be a 5.1 system.
- Carsten
The common cinema audio processors have switches/cue options to change their channel assignments between 5.1 and 7.1. Typically, for 5.1, the side surrounds get copied to the back surrounds, and all surrounds are slightly reduced in level to get the same surround balance as in 5.1 only systems.
All cinema processors are 5.1 initially. 7.1 then is an option to setup, and once configured, there are means to switch between the standard 5.1 and the extra 7.1 config.
As for commercial movie releases, the majority is in 5.1. When there is a 7.1 version available, then a 5.1 version is made available as well.
E.g. for an international movie, we usually receive an OV version in english, and e.g. a 5.1-VF in german and a 7.1-VF in german.
Movie trailers come in 5.1 only (with some very few exceptions).
I f you play a 7.1 DCP on a 5.1 system, the back surround channels will not be audible. I don't know any cinema processor that allows to mix rear surrounds to side surrounds. Wouldn't make sense anyway, since, if a processor would have access to rear surround channels, it would necessarily be a 7.1 capable processor. And so it wouldn't be a 5.1 system.
- Carsten
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flmmkr
- Posts: 8
- Joined: Sun Jun 11, 2017 7:07 am
Re: 5.1 vs 7.1 surround
Carsten, thank you for replying. Sounds like we should be okay with our 5.1 mix then.
This reinforces my theory that there was something wrong with the theater or the people operating it at that time.m. This was for a festival and we were told the theaters usual projectionists were not running things and the festival had their own people in the projection rooms.
While our movie was playing we didn't hear sound from the surrounds and it seemed like all the music (pretty much all that was in the surrounds for this movie) were playing in the right front speaker. I was sitting about 3 seats to the right of dead center.
When we were discussing what we experienced with them, they took us into the same theater while the next movie was playing. It was a stereo mix. We were more to the right of the screen, and still heard only audio from the right speaker. He said this was likely do to being a near-field mix and/or a phase issue or discrete vs. true stereo mix.
They took us into the projection room and showed us the audio system. They said it was a Dolby CP850. I saw on the processor display that it said "Dolby 5.1 + Atmos" which seemed odd to me as I would have expected it to say "Stereo" since it was a stereo mix.
Our mix isn't done by an amateur or anything so I'd be surprised it was an issue with our mix. Is this something the theater/projectionists likely messed up with?
This reinforces my theory that there was something wrong with the theater or the people operating it at that time.m. This was for a festival and we were told the theaters usual projectionists were not running things and the festival had their own people in the projection rooms.
While our movie was playing we didn't hear sound from the surrounds and it seemed like all the music (pretty much all that was in the surrounds for this movie) were playing in the right front speaker. I was sitting about 3 seats to the right of dead center.
When we were discussing what we experienced with them, they took us into the same theater while the next movie was playing. It was a stereo mix. We were more to the right of the screen, and still heard only audio from the right speaker. He said this was likely do to being a near-field mix and/or a phase issue or discrete vs. true stereo mix.
They took us into the projection room and showed us the audio system. They said it was a Dolby CP850. I saw on the processor display that it said "Dolby 5.1 + Atmos" which seemed odd to me as I would have expected it to say "Stereo" since it was a stereo mix.
Our mix isn't done by an amateur or anything so I'd be surprised it was an issue with our mix. Is this something the theater/projectionists likely messed up with?
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Carsten
- Posts: 2804
- Joined: Tue Apr 15, 2014 9:11 pm
- Location: Germany
Re: 5.1 vs 7.1 surround
Hmm. You would think that an ATMOS equipped screen would be setup properly. Well, in this case, the people dealing with the system obviously didn't know much. The CP850 is able to play 5.1, 7.1 and ATMOS. 'Real' stereo mixes can be played in both 5.1 and 7.1 - there will only be signal on L and R, and the system doesn't care wether there is actual sound or digital silence on all other channels.
Some cinema processors have per channel VU meters, so you can easily see what signal plays where. Unfortunately, the CP850 doesn't offer it on the main unit display. Under these conditions, everything is possible - they may even have forgotten to switch on all the amps.
The CP850 does not switch automatically to different formats, so you shouldn't expect it to display '7.1' just because you are playing a 7.1 feature. There is little automation going on in cinemas for video and audio formats. The projectionist has to get the control cues right when setting up the content playlist. If he misses the 7.1 cue towards the processor, the feature will play in 5.1, and thus the back surround signals of the DCP will be missing.
I suggest you get a standard test DCP for 5.1 and 7.1 - one from Dolby floats around the net. If you feel unsafe, play it and listen in the auditorium wether all channels are audible and come from the right direction. And the name Dolby on screen may impress them enough to take a deeper look wether there is something screwed.
- Carsten
Some cinema processors have per channel VU meters, so you can easily see what signal plays where. Unfortunately, the CP850 doesn't offer it on the main unit display. Under these conditions, everything is possible - they may even have forgotten to switch on all the amps.
The CP850 does not switch automatically to different formats, so you shouldn't expect it to display '7.1' just because you are playing a 7.1 feature. There is little automation going on in cinemas for video and audio formats. The projectionist has to get the control cues right when setting up the content playlist. If he misses the 7.1 cue towards the processor, the feature will play in 5.1, and thus the back surround signals of the DCP will be missing.
I suggest you get a standard test DCP for 5.1 and 7.1 - one from Dolby floats around the net. If you feel unsafe, play it and listen in the auditorium wether all channels are audible and come from the right direction. And the name Dolby on screen may impress them enough to take a deeper look wether there is something screwed.
- Carsten