audio_replacement/
audio_replacement.rs

1//! Replace the audio track of a video file without re-encoding video.
2//!
3//! Uses [`AudioReplacement`] to mux the video stream from one file with the
4//! first audio stream from another file using stream-copy (no decode/encode
5//! cycle).  The video quality is preserved exactly and the operation is fast.
6//!
7//! # Usage
8//!
9//! ```bash
10//! cargo run --example audio_replacement -- \
11//!     --video  original.mp4  \
12//!     --audio  new_audio.mp3 \
13//!     --output replaced.mp4
14//! ```
15
16use std::process;
17
18use ff_remux::AudioReplacement;
19
20fn main() {
21    let mut args = std::env::args().skip(1);
22    let mut video = None::<String>;
23    let mut audio = None::<String>;
24    let mut output = None::<String>;
25
26    while let Some(flag) = args.next() {
27        match flag.as_str() {
28            "--video" | "-v" => video = Some(args.next().unwrap_or_default()),
29            "--audio" | "-a" => audio = Some(args.next().unwrap_or_default()),
30            "--output" | "-o" => output = Some(args.next().unwrap_or_default()),
31            other => {
32                eprintln!("Unknown flag: {other}");
33                process::exit(1);
34            }
35        }
36    }
37
38    let video = video.unwrap_or_else(|| {
39        eprintln!("Usage: audio_replacement --video <file> --audio <file> --output <file>");
40        process::exit(1);
41    });
42    let audio = audio.unwrap_or_else(|| {
43        eprintln!("--audio is required");
44        process::exit(1);
45    });
46    let output = output.unwrap_or_else(|| {
47        eprintln!("--output is required");
48        process::exit(1);
49    });
50
51    println!("Video source: {video}");
52    println!("Audio source: {audio}");
53    println!("Output:       {output}");
54    println!();
55    println!("Replacing audio track (stream-copy, no re-encode)…");
56
57    AudioReplacement::new(&video, &audio, &output)
58        .run()
59        .unwrap_or_else(|e| {
60            eprintln!("Error: {e}");
61            process::exit(1);
62        });
63
64    let size = match std::fs::metadata(&output) {
65        Ok(m) => {
66            #[allow(clippy::cast_precision_loss)]
67            let kb = m.len() as f64 / 1024.0;
68            if kb < 1024.0 {
69                format!("{kb:.0} KB")
70            } else {
71                format!("{:.1} MB", kb / 1024.0)
72            }
73        }
74        Err(_) => "(unknown size)".to_string(),
75    };
76
77    println!("Done. {output}  {size}");
78}
audio_replacement/audio_replacement.rs

audio_replacement/
audio_replacement.rs
