Objective

Encode and mux assets for video files ensuring compatibility with iOS 26+ and macOS 26+ (Tahoe).

This includes:

• Embedding subtitles in Apple’s tx3g format.
• Incorporating chapter markers with both text labels and thumbnail images.

1. Chapter Metadata Specification

To ensure chapters are recognized, the metadata file must follow the FFMETADATA header format with timestamps in nanoseconds (or based on timebase).

Since last essay, we have known the basic concepts of media files. Then we need to solve some real-world problems by using the command-line tool ffmpeg.

Overview

Before we gets our hands on the actual commands, let us review the procedure of FFmpeg processing media files:

 _______              ______________
|       |            |              |
| input |  demuxer   | encoded data |   decoder
| file  | ---------> | packets      | -----+
|_______|            |______________|      |
                                           v
                                       _________
                                      |         |
                                      | decoded |
                                      | frames  |
                                      |_________|
 ________             ______________       |
|        |           |              |      |
| output | <-------- | encoded data | <----+
| file   |   muxer   | packets      |   encoder
|________|           |______________|

Refer to FFmpeg - Documentation

Did you once meet the situation that you wanted to upload some videos you just edited to some website, but told the format is not supported? Or you once wanted to play some video you just downloaded, but told the format is not supported by the video player? Then we may need the help of FFmpeg to solve that issue.

Method 1: Screen Recording

在 CPU 性能足够的情况下，可以通过录制屏幕的方式来获得 LibCACA 输出的 ASCII 视频

1. List Devices

列举出 AVFoundation 的输入设备

ffmpeg -f avfoundation -list_devices true -i ""

2. Rec Screen

在第一步的基础上，使用 FFmpeg 选择需要的输入设备进行录制

# e.g.
ffmpeg -y -f avfoundation \
-i 1:3 -framerate 30 \
-c:v libx264 -r 30 -pix_fmt uyvy422 \
-preset slow -crf 19 \
-c:a aac -b:a 192k \
"$INPUT $(date "+%Y-%m-%d %H-%M-%S").mp4"

* Rec Terminal

另一种办法是录制终端字符，在此使用现成的终端录制项目: