Correctly recode PAL 25fps dvds to standard 23.976 fps

MKV playback, recompression, remuxing, codec packs, players, howtos, etc.
Post Reply
Krawk
Posts: 146
Joined: Thu Jul 02, 2015 12:10 am

Correctly recode PAL 25fps dvds to standard 23.976 fps

Post by Krawk » Thu Mar 22, 2018 4:22 am

Many American TV shows are shot in 24fps, or more correctly 23.976, and when they're mastered for the UK, the studio will often do it the lazy way and simply speed up playback to match the 25fps data rate. Converting this back is actually not too hard with the right tools. You can choose to leave the files on your media server or hard drive at 25fps and if you've got a really good playback device it will correctly slow the frame rate down and lower the pitch of the audio as well. But what if your playback device is not so good or you just simply want to store these files back in their proper original format? Even if it seems as though you thought you changed the files to 23.976, look a little closer and tell me there aren't artifacts of some sort, such as dropped frames. You can look around on the internet for help but you will run into the same outdated, incorrect information as I did. You will find dead links, programs that do not work on anything beyond Windows XP, and so on. In my example here, I am using a Windows 10 machine, but I think the same 3 programs are available for other platforms as well. OK, so without further adieu, here we go. I will assume you are going to use the same programs I do, if not, the concept is still the same.

1) Rip your discs with MakeMKV. Most TV show dvds are 1 episode per title, and typically your rips will be the same order as the episodes are on the disc. You can verify this yourself after ripping. TIP: If you use a program such as VLC after MakeMKV has completed the rip, regardless of region code and such on the disc, it will work.
-- In this example we will say Title01.mkv is the file we wish to work with.

2) Load MKVToolnix.
a) Within the Multiplexer tool, open Title01.mkv. You are going to multiplex 2 copies of the same input file but here's what you need to do. First, in the lower pane, deselect (uncheck) all the tracks except the audio track. Click start multiplexing and very shortly you should see another file named Title01.MKA in your working directory. Next, uncheck the audio track and check (enable) the video track and anything else you want to keep. Click/highlight the actual video track in the lower pane, then on the right where it says Default Duration/FPS, select 24000/1001P. Again, click Start Multiplexing. You should see Title01 (1).mkv shortly. (I have not personally checked to see if subtitles remain in sync as I do not use them. If they do lose sync, you probably have to also do the same thing with the sub tracks as well, 24000/1001P)
b) Close your original MKV
c) Select the Info Tool within MKVToolnix. Load the newly created video Title01 (1).mkv. You're looking specifically for Duration of this track. In my example it was 00:24:03.565000000

3) Load an audio editor app. I use Audacity as it is an excellent shareware tool.
a) Select Import Audio and locate Title01.MKA (you might have to select "all files" on the file types of the load file dialog) - If the program tells you that you need to download the FFMPEG plugin, proceed to do so via the link it provides. If the program doesn't know what an MKA file is, you can rename the file to have a .ac3 extension instead, then it will prompt you to download ffmpeg plugin. The next time you use an MKA file afterwards though you do not need to rename it as the FFMPEG plugin will recognize the file type.
b) Make sure your sample rate is correct on the main screen. For dvd audio it should pretty much always be 48000hz. You can poke around other options if you wish, such as bitrates but you should not need to touch them unless you want to lower the bitrates.
-Under "Effect" select the "Change Speed" option. Because of the various obstacles, it is best to simply choose the correct duration rather than a fixed percentage. In my example here, I ensure it is 00:24:03.565 - Note that Audacity does not have the extra decimal points beyond that like you saw above in line 2c. Every time I have done this, the extra decimals have always been zeroes anyway.
c) Select ok and Audacity will process the sample.
d) Select Export audio from the File menu. It is perfectly acceptable to allow the program to use the default file extension, so save it as title01.ac3 - If you really want to use the MKA extension, save it over itself or use another name

4) Return back to MKVToolnix. Close out the info tool or just switch back to the Multiplexer. If there's something already there, close the project with the red X.
a) Now, choose New and then click add files -(still using my examples) click title01.ac3 and (hold control if you need to in order to select 2 files at once) Title01 (1).mkv
b) Click Start Multiplexing. You should see another file in a few moments, this time named Title01 (1)(1).mkv

At this point you should be able to fully manipulate Title 01 (1)(1).mkv with recoding tools like Handbrake, playback software or devices that cannot convert PAL to NTSC. Remember too that standardized video for dvd is 720 x 480 so if you recode it with Handbrake, select that resolution on the main screen and Handbrake should adjust the PAR automatically.
I also encourage you to load Title01 (1)(1).mkv and then Title01.mkv and observe the difference in audio. The final file we just created here should sound better. You don't realize there is a shift in pitch until you hear both versions. If you use a program such as MPC-HC you can select Properties while each MKV is playing back and you should see the fps has changed but everything else, including the audio should be the same.

Krawk
Posts: 146
Joined: Thu Jul 02, 2015 12:10 am

Re: Correctly recode PAL 25fps dvds to standard 23.976 fps

Post by Krawk » Thu Mar 22, 2018 4:25 am

I am happy to answer any questions I can, and I will edit the first post as needed.
I created the post because much of what's out there seems to be from 2008 or older. Anything newer involves commercial software, software that doesn't work as advertised or command line programs that many of us wouldn't have a clue what to enter for commands. I know my way around a CLI - my first computer was in the 80's so I am used to a DOS type environment. Not saying it'd better or less confusing though!

Post Reply