Converting Dolby audio tracks to plain stereo

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cadcoke5
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Joined: Sun Jan 17, 2021 8:24 pm

Converting Dolby audio tracks to plain stereo

Post by cadcoke5 »

I am attempting to get a Blu-ray movie into a format where I can edit it in HitFilms Express (a video editing program). It recognizes the m2st file and the video. But, the 1st sound track is in 6-channel Dolby, and that is creating a problem. The 2nd channel is [edit, NOT stereo. It is 4-track] Dolby Digital, but the same issue is there. The Dolby tracks don't come successfully into HitFilms. I've tried using MakeMKV just to get the audio track into an MP3, and then later to merge it with the video. But the results were a sound track that sounded quite garbled. I've also tried VLC Media Player, with the same results. Though, the non-Dolby Spanish channel comes out OK.

Here is a bit of the back-story...
I am attempting to create a set-up to show some Cinerama films in the original format, using 3 video projectors onto a curved screen. I have a video card that can drive up to 4 monitors, and present itself to Windows as a single monitor. I have a Blu-ray of "The Robe", but it is in letter box. If I stretch the video player to be as wide as the 3 projectors, then I get letter boxes on the sides.

Any ideas for me to try?
Woodstock
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Re: Converting Dolby audio tracks to plain stereo

Post by Woodstock »

That software seems awfully deficient in capabilities...

As far as audio, programs like Audacity and ffmpeg will allow you to convert between formats quite easily. MKVToolnix can split up an MKV file into its constituent parts, and even merge them back together later.

But MakeMKV is limited in what it will do during a rip. You can convert DTS to FLAC, AAC, or AC3. But you're better off using separate tools, so that you can make finer choices on how to do the mix-down.
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dcoke22
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Re: Converting Dolby audio tracks to plain stereo

Post by dcoke22 »

The Robe (https://en.wikipedia.org/wiki/The_Robe_(film)), from 1953, was filmed in CinemaScope (https://en.wikipedia.org/wiki/CinemaScope), which was a single camera, single projector system, albeit one that used anamorphic lenses and allowed for an image much wider than what was common at the time.

You might consider the two-disc, SmileBox version of How the West Was Won (https://www.blu-ray.com/movies/How-the- ... 42/#Review). It was (mostly) filmed in 3-strip Cinerama (https://en.wikipedia.org/wiki/Cinerama) and has been given a decent presentation by Warner Brothers.

You might also consider using something like Adobe Premiere Pro, which is professional level video editing software. I doubt you'd run into audio format problems (but I'm not proficient with Premiere, so I'm just guessing). It has a free trial and is about $20/month, so the entry fee is low.

edit: I also wonder if you could just 'stretch' your playback window across all three screens without trying to crop the video into 3 separate streams?
cadcoke5
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Joined: Sun Jan 17, 2021 8:24 pm

Re: Converting Dolby audio tracks to plain stereo

Post by cadcoke5 »

I've read about the development of Cinerama and CinemaScope, though sometimes I forget which is which. Regardless of if multiple cameras were used, the DVDs are a single image. I considered using an anamorphic lens, though I have not been able yet to find that format, only the letter box. I was curious about how they would handle the format that was originally designed for a curve screen. And I see that they warped it to some extent to make it look good on a flat screen, that may mean that I can't just show it onto a curved screen without their warp now becoming incorrect.

The reason I decided to use 3 projectors, is that I can get used ones cheap. An XGA 1024x768, 2000 lumen projector is now only $50. I already have a video card capable of dividing out the virtual desktop among the 3 projectors. Nvidia now offers a "Moasic" mode, where it presents itself to windows as though it were a single desktop, and it works with regular Windows Media Player. If I try the letter box version, and stretch the window out amont the 3 projectors, Windows will introduce more letter box squares on the left and right. So, that is why I need to edit out the letter box entirely.

In my experiments with the projectors, the differing focal distance is not an issue for the amount of curve each projector needs to cover.

-Joe
cadcoke5
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Joined: Sun Jan 17, 2021 8:24 pm

Re: Converting Dolby audio tracks to plain stereo

Post by cadcoke5 »

Woodstock, thank you for the suggestion. But, Audacity didn't recognize the m2ts file at all. I tried both just opening the file without specifying a file type, and import raw. Import raw brought data in, but the sound is pure gibberish noise.

I looked for ffmpeg, but am quite confused about what file to get and install. There seem to be a zillion possible files. Even when I choose a link to a windows installer, it still gives me a the same zillion possible files to download.

If I am correct, ffmpeg is not a program with a user interface, but rather is used from the command line. Am I right?
Woodstock
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Joined: Sun Jul 24, 2011 11:21 pm

Re: Converting Dolby audio tracks to plain stereo

Post by Woodstock »

Yes, "raw" ffmpeg is a command line program, but there are "graphic user interfaces" available for it.

Your initial message didn't say you were working with the m2ts files, so I ass-u-me-d you were dealing with MKV files. Audacity can extract audio out of those. ffmpeg works with dozens of container types.
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dcoke22
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Re: Converting Dolby audio tracks to plain stereo

Post by dcoke22 »

It doesn't surprise me that Windows introduces black on the left and right of your '3 projector' setup. When all three of those 1024x768 are setup together, they produce a window that is effectively 3072 pixels wide and 768 high. That ends up being a ratio of 4:1; it is 4 pixels wide for every 1 pixel it is high. A standard widescreen TV these days 16:9, or 16 pixels wide for every 9 high. 1920x1080 (standard HD resolution) works out to 16:9 or about 1.77:1. So, Your '3 projector' setup is way, way wider than a standard HD TV.

As an example, let's look at the movie 1917 (https://www.blu-ray.com/movies/1917-4K-Blu-ray/259242/). If you watch it on a HD TV, there will be black bars at the top and bottom because the movie was shot in a wider format than 1.77:1 (aka 16:9). It was shot in 2.39:1. To say it another way, for every 1 pixel of height, it'll be 2.39 pixels across. So, if you want to squeeze all that width onto your HD TV you won't use all the height; hence the black bars at the top and bottom.

A Cinerama film, like How the West Was Won (https://www.blu-ray.com/movies/How-the- ... ray/17169/) has an aspect ratio of 2.89:1, meaning it is even wider than 1917. It is a very wide film. CinemaScope films, like The Robe, were 2.66:1.

But all of this a long winded way of saying, if you're using 3 1024x768 projectors stitched together to effectively make a single 3072x768 screen, your screen is wider than any film. As such, if you use all 768 pixels of height, nothing is wide enough to fill up all 3072 pixels of width. Even if you use something like Handbrake to chop off the letterbox bars (top & bottom) included on the blu-ray intended for your 16:9 HD TV. (You could always distort the image and make people look weird, but I don't think that's what you're trying to do.)
cadcoke5
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Re: Converting Dolby audio tracks to plain stereo

Post by cadcoke5 »

Yes, I realize that my screen is too wide. There will be some overlap for blending, perhaps 20 pixels per projector. Still, it will be much wider than necessary. But, I didn't want to use two projectors, because then the seam would be in the middle. I had considered turning the projectors on their sides. But, the image offset would be in the wrong spot, and my projector would have to be elevated halfway up the height of my screen.

I also have the goal of doing a wide image, for some creation related content. I am planing to do 180 deg of wrap-around screen. But, I will have to create that content myself.

-Joe
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