Film-Tech Forum ARCHIVE: DCP-o-Matic audio only?

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Posted by Stephen Furley (Member # 1277) on 03-10-2016, 09:03 AM:

Is it possible to create a DCP containing only audio with DCP-o-Matic? Alternatively, is it possible to create one from two separate files, one a bitmap of a single black frame, and the other containing the audio?

It's to enable me to play an overture and entr'acte, which at the moment are on my iPod, without having to actually use the iPod during the show.

Posted by Fernando Caldeira (Member # 5680) on 03-10-2016, 09:33 AM:

I´ve done that.
Used Moviemaker with a black frame and added the mp3 audio file. Then made de DCP using DCP-o-matic. [Smile]

There are probably more professinal ways to do it, but this works!

Cheers
Fernando

Posted by Stephen Furley (Member # 1277) on 03-10-2016, 10:07 AM:

Thanks, I'll try it tonight.

Posted by Carl Hetherington (Member # 7107) on 03-10-2016, 11:59 AM:

I don't think you need to add a black frame; just add the audio and everything should be ok. I haven't tested it mind you.

Posted by Carsten Kurz (Member # 5396) on 03-10-2016, 12:00 PM:

quote: Stephen Furley
Is it possible to create a DCP containing only audio with DCP-o-Matic? Alternatively, is it possible to create one from two separate files, one a bitmap of a single black frame, and the other containing the audio?

You don't need black frame source footage. DCP-o-matic fills in everything that is needed to make the DCP compliant. So, just import your audio, make the necessary format choices, hit 'Make DCP', and DCP-o-matic will automatically create black frames for as long as the audio lasts.

You can even import and create subtitles without any image or audio. Just import a subtitle file, 'Make DCP', and DCP-o-matic will create silent audio and black for as long as the subtitles go.

Now that all sounds very convenient - but keep in mind that due to a library license issue, DCP-o-matic will not import MP3 or AAC audio as your overture, you need to convert it into another supported format before - e.g. WAV or AIFF.

- Carsten

Posted by Leo Enticknap (Member # 534) on 03-10-2016, 04:47 PM:

quote: Carsten Kurz
DCP-o-matic will not import MP3 or AAC audio as your overture...

It was a few versions ago now, but I did create a DCP ripped from a DVD title, which had Dolby AC3 audio only. It wouldn't play any audio when previewing in DCP-o-Matic, but the audio level graph worked and the audio was present and correct on the rendered DCP.

Maybe there was a pre-existing codec installed on my computer that DCP-o-Matic used to transcode the audio?

Posted by Carsten Kurz (Member # 5396) on 03-10-2016, 05:20 PM:

Embedded audio codecs in interleaved video files have never been a problem. It's only a problem with the mentioned audio-only formats. You'll get an error when trying to import an MP3 or AAC file. Which is what many people will try at first when composing a static background from a still with some music from their MP3 collection. No big deal once you know it, but at first people are stunned that something as basic as an MP3 file is not supported.

Yes, there never has been audio play/preview in DCP-o-matic, and according to Carl, it is not easy to do, at least not with the multi-plattform approach of DCP-o-matic.

- Carsten

Posted by Carl Hetherington (Member # 7107) on 03-10-2016, 05:21 PM:

quote: Leo Enticknap
It was a few versions ago now, but I did create a DCP ripped from a DVD title, which had Dolby AC3 audio only. It wouldn't play any audio when previewing in DCP-o-Matic, but the audio level graph worked and the audio was present and correct on the rendered DCP.

It's a bit (unnecessarily) complicated. Video+audio files e.g. DVD rips are decoded by FFmpeg (which supports AAC and MP3) but audio-only files e.g. WAV/AIFF are decoded by libsndfile (which does not support AAC nor MP3).

Really FFmpeg should probably do both.

quote: Carsten Kurz
Yes, there never has been audio play/preview in DCP-o-matic, and according to Carl, it is not easy to do, at least not with the multi-plattform approach of DCP-o-matic.

Yes, there's a few reasons why I have avoided it:

the need for a multi-platform audio playback library (though they exist, this is really just an excuse!)
at the moment video is previewed with fairly casual timing (if the frame rate is not quite right, who cares) but once you have audio you have to get video/audio sync right, even if video is being decoded way below realtime (e.g. when previewing existing DCPs)
what to do with multichannel audio on stereo systems
"why is the audio so quiet?"

But there have been a few people surprised by a lack of audio in the preview lately, and I can see how it would be useful when choosing from different language soundtracks. I really should just get on with it [Wink]

Posted by Carsten Kurz (Member # 5396) on 03-11-2016, 08:34 AM:

Maybe it is possible to add a basic audio play function in the audio analysis window, just for inspection purposes, so the sync issue goes away. You could also enable individual channels there as you do now for the level display. That would be enough to identify channels/languages.

- Carsten

Posted by Pietro Clarici (Member # 4937) on 03-11-2016, 08:53 AM:

Having botched up a couple of DCPs after selecting the wrong audio track, I think a quick and dirty way to play a few seconds and check would be useful.

Another (probably more complicated) way to solve this: DCP-o-matic could wrap all the audio tracks it can find and create different CPLs with the same video track, so a single encode would generate all language versions at the same time.

Posted by Leo Enticknap (Member # 534) on 03-12-2016, 10:32 PM:

Even if it didn't automatically wrap them all, the option to create an OV using one, and then VFs using one or more of the others, all in the same operation, would definitely be useful.

Posted by Pietro Clarici (Member # 4937) on 03-13-2016, 06:07 PM:

Exactly, OV + VF in a single process is what I was suggesting.
By "wrapping" I just meant generating multiple MXF audio files.

Posted by Monte L Fullmer (Member # 2797) on 03-16-2016, 04:41 AM:

One could make some preshow/intermission background music with this technique...add this CPL in the SPL build at the beginning since it will have no cues for bulb strike, dowser opening and light control ...

-Monte

Posted by Monte L Fullmer (Member # 2797) on 03-17-2016, 02:17 PM:

UPDATE: made a test clip with audio at -12dB on the audio settings before conversion and it works great.

-12dB matches the audio output with the feature. I recorded the source with the VU meters close to -3dB at loudness peak

thx - Monte

Posted by Stephen Furley (Member # 1277) on 04-19-2016, 08:09 AM:

Thanks for the advice; it worked fine.

Posted by Yinghong Wu (Member # 6908) on 04-21-2016, 08:06 PM:

I have six mono wave files.I want to make a 5.1 audio DCP,What shall i do.

Posted by Bajsic Bojan (Member # 4928) on 04-22-2016, 02:50 AM:

dcpomatic - import them, on dcp/audio tab select 5.1 sound, no processing, go to content/audio tab and select on which channel a specific wav file should play (green squares), make dcp

opendcp - mxf tab, select type: WAV, sound input mono, output 5.1, select files for specific channels, make mxf, make dcp