README

This repository provides kinds of shell scrips to help you convert media that may be not well-supported on macOS. The most important one is mkv_to_mp4.sh, converting mkv files with HEVC/AVC and FLAC codec.

Author: Yang-Xijie https://github.com/Yang-Xijie

If you want to figure out how to use this script and how to create MAD with the best quality, check serial tutorials on Bilibili (Chinese).

• README
• Convert BDrip(.mkv) to mp4(.mp4)
  • Background
  • Function
  • How to Use it
  • Discussion
    • ffmpeg and -vtag
    • modify the script if necessary
    • transcode in FCP to better your video editing experience
• Other Scrips
  • Convert BDMV(.m2ts) to mov
    • Function
  • Convert FLAC(.flac) to ALAC(.m4a)
    • Function
    • Discussion
• Note

Convert BDrip(.mkv) to mp4(.mp4)

Background

Sometimes we want to create our own MAD using great clips in some animation. We download the resources (often BDrip because it's rather smaller than BDMV and with great quality) from BT or PT sites or somewhere else. But these files have a container mkv (often with HEVC (video) and FLAC (audio) codec) which is unable to import into FCP (because mkv is not an official container format).

To convert BDrip, one way is to transcode it. However, to extrat and re-package them into a compatitable continer is much more efficient and keep the original quality. This script is to realize it.

Function

Convert anime BDrip (with mkv container format, track 0 HEVC, track 1 FLAC) to mp4 in order to make it importable in FCP without transcoding (just extract and re-package). (Note: also importable in Compressor so that you can further convert it to other codecs that are well-supported on macOS such as Apple Prores.)

How to Use it

• (Once) Get the script mkv_to_mp4.sh: download the zip of this repo / clone this repo / open the script on GitHub and copy the content to a newly created text file and rename it
• (Once) Make the script executable: run command chmod +x mkv_to_mp4.sh.
• (Once) Install the required tools: run command brew install mkvtoolnix ffmpeg mp4box. (brew, one of the best package managers for macOS, should be installed before. Run command brew update before installing new packages.)
• Change the shell working directory to the folder with mkv files: run command cd <folder>. Check the codec of mkv tracks -- this script only supports track 0 HEVC(h265), track 1 FLAC. To convert mkv files with AVC(h264) codec, change all h265 to h264 in this script.)
• Copy the script to the current directory.
• Run the script: run command ./mkv_to_mp4.sh.

Discussion

ffmpeg and -vtag

Theoretically command ffmpeg -i <input>.mkv -vcodec copy -acodec alac <output>.mp4 works. But FCP cannot import the <output>.mp4 for its restriction on the description of video codec. (check StackExchange | Reason for -vtag and Apple Developer Documentation | HLS Authoring Specification for Apple Devices | Video 1.10 for more information).

Moreover, if you use command ffmpeg -i <input>.mkv -map 0:0 -map 0:1 -vcodec copy -acodec alac -vtag hvc1 "<output>.mov", the frame-rate goes wrong (from 23.98 to 23.81, CFR to VFR). (check reddit | Framerate issue in fcp (23.98-23.81 FPS) for more information). That ffmpeg doesn't obey standard mp4 boxing might be the reason.

modify the script if necessary

You should make slight adjustment in the script if your media has a codec different from mkv format, track 0 HEVC, track 1 FLAC.

transcode in FCP to better your video editing experience

(after importing mp4 files into FCP) For editing in FCP, it's better to use Apple Prores to make rendering faster. Choose proxy in FCP if your Mac lacks performance, or transcode the media to Apple Prores 422.

Notice Import output files (.mp4) directly into FCP because they have the original quality. Don't transcode them using other apps which may decrease the quality. (converting to Apple Prores 422 HQ / 422 just slightly decrease quality and it's convenient if you have a workflow with large storage. To learn more, check Apple Prores White Paper.)

Other Scrips

Here are some other scripts that convert specific kinds of media.

Convert BDMV(.m2ts) to mov

BDMV owns the best quality of anime. Convert them to mov in order to import them into FCP with the best quality.

Function

Convert BDMV anime (with m2ts format, track 0 H264/AVC, track 1 PCM) to mov in order to make it importable in FCP without transcoding.

Convert FLAC(.flac) to ALAC(.m4a)

FLAC is a codec for lossless audio. However, FCP or Compressor (and also Music.app) doesn't support that not-for-industry audio codec.

ALAC is a codec for lossless audio designed by Apple. So it has a great support in macOS.

Function

The function of this script is to convert FLAC file (with a suffix .flac) to ALAC (with a suffix .m4a).

Discussion

You may think command ffmpeg -i song.flac -acodec alac song.m4a or ffmpeg -i song.flac song.m4a is enough. But unfortunately sometimes it fails. Check Stack Overflow for details.

Note

• English is not my native language; please excuse typing errors. Suggestions on my expression is welcome!
• Any advice or discussion will be appreciated!