viser_ffmpeg/
encode.rs

1use std::path::{Path, PathBuf};
2use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
3use tokio::io::AsyncBufReadExt;
4use tokio::process::Command;
5
6use crate::{Codec, RateControlMode, Resolution, ffmpeg_path, probe};
7
8/// Parameters for a single encode.
9#[derive(Debug, Clone)]
10pub struct EncodeJob {
11    /// Source media file path.
12    pub input: String,
13    /// Destination file path for the encoded output.
14    pub output: String,
15    /// Optional target resolution; when set, scales with the lanczos filter.
16    pub resolution: Option<Resolution>,
17    /// Video codec to encode with.
18    pub codec: Codec,
19    /// Constant rate factor / quantizer value (interpretation depends on `rate_control`).
20    pub crf: i32,
21    /// Rate-control mode that determines how `crf`/bitrate fields are applied.
22    pub rate_control: RateControlMode,
23    /// Target bitrate in kbps; used for VBR mode.
24    pub target_bitrate: f64, // kbps, used for VBR mode
25    /// Maximum bitrate cap in kbps; used for capped CRF mode.
26    pub max_bitrate: f64, // kbps, used for capped CRF mode
27    /// VBV buffer size in kbps; used for capped CRF mode.
28    pub bufsize: f64, // kbps, used for capped CRF mode
29    /// Encoder speed preset (e.g. `"medium"`); empty leaves the encoder default.
30    pub preset: String,
31    /// Extra raw FFmpeg arguments appended verbatim before the output path.
32    pub extra_args: Vec<String>,
33}
34
35/// Output of a completed encode.
36#[derive(Debug, Clone)]
37pub struct EncodeResult {
38    /// The job that produced this result.
39    pub job: EncodeJob,
40    /// Average bitrate of the output in kbps, measured by probing it.
41    pub bitrate: f64, // kbps (average)
42    /// Output file size in bytes.
43    pub file_size: u64, // bytes
44    /// Wall-clock time taken to encode.
45    pub duration: Duration, // wall-clock encode time
46}
47
48/// Real-time encoding progress info parsed from FFmpeg.
49#[derive(Debug, Clone, Default)]
50pub struct Progress {
51    /// Number of frames encoded so far.
52    pub frame: i64,
53    /// Current encoding rate in frames per second.
54    pub fps: f64,
55    /// Current output bitrate in kbps.
56    pub bitrate: f64, // kbps
57    /// Encoding speed relative to real time (e.g. 2.5 means 2.5x).
58    pub speed: f64, // e.g. 2.5x
59    /// Output timestamp reached so far.
60    pub time: Duration,
61}
62
63/// Runs an FFmpeg encode job. Progress updates are sent on the channel if provided.
64pub async fn encode(
65    job: EncodeJob,
66    progress_tx: Option<tokio::sync::mpsc::Sender<Progress>>,
67) -> anyhow::Result<EncodeResult> {
68    match job.rate_control {
69        RateControlMode::Vbr => encode_two_pass(job, progress_tx).await,
70        _ => encode_single_pass(job, progress_tx).await,
71    }
72}
73
74async fn encode_single_pass(
75    job: EncodeJob,
76    progress_tx: Option<tokio::sync::mpsc::Sender<Progress>>,
77) -> anyhow::Result<EncodeResult> {
78    let args = build_encode_args(&job, EncodePass::Single)?;
79    run_encode(job, args, progress_tx).await
80}
81
82async fn encode_two_pass(
83    job: EncodeJob,
84    progress_tx: Option<tokio::sync::mpsc::Sender<Progress>>,
85) -> anyhow::Result<EncodeResult> {
86    if job.target_bitrate <= 0.0 {
87        anyhow::bail!("target bitrate must be greater than zero for VBR mode");
88    }
89
90    let passlog_prefix = make_passlog_prefix(&job.output);
91    let cleanup = PasslogCleanup::new(passlog_prefix.clone());
92
93    let first_pass_args = build_encode_args(&job, EncodePass::First(&passlog_prefix))?;
94    run_ffmpeg(first_pass_args, None).await?;
95
96    let second_pass_args = build_encode_args(&job, EncodePass::Second(&passlog_prefix))?;
97    let result = run_encode(job, second_pass_args, progress_tx).await;
98
99    cleanup.run();
100    result
101}
102
103async fn run_encode(
104    job: EncodeJob,
105    args: Vec<String>,
106    progress_tx: Option<tokio::sync::mpsc::Sender<Progress>>,
107) -> anyhow::Result<EncodeResult> {
108    let start = Instant::now();
109    run_ffmpeg(args, progress_tx).await?;
110
111    let elapsed = start.elapsed();
112
113    // Probe the output to get actual bitrate and file size
114    let meta = std::fs::metadata(&job.output)
115        .map_err(|e| anyhow::anyhow!("failed to stat output: {e}"))?;
116
117    let probe_result = probe(&job.output).await?;
118    let bitrate = probe_result.format.bit_rate as f64 / 1000.0;
119
120    Ok(EncodeResult { job, bitrate, file_size: meta.len(), duration: elapsed })
121}
122
123async fn run_ffmpeg(
124    args: Vec<String>,
125    progress_tx: Option<tokio::sync::mpsc::Sender<Progress>>,
126) -> anyhow::Result<()> {
127    let mut cmd = Command::new(ffmpeg_path());
128    cmd.args(&args).stdout(std::process::Stdio::piped()).stderr(std::process::Stdio::piped());
129
130    let mut child = cmd.spawn().map_err(|e| anyhow::anyhow!("failed to start ffmpeg: {e}"))?;
131
132    // Parse progress from stdout
133    if let Some(stdout) = child.stdout.take() {
134        let tx = progress_tx.clone();
135        tokio::spawn(async move {
136            let reader = tokio::io::BufReader::new(stdout);
137            let mut lines = reader.lines();
138            let mut p = Progress::default();
139            while let Ok(Some(line)) = lines.next_line().await {
140                if parse_progress_line(&line, &mut p)
141                    && let Some(ref tx) = tx
142                {
143                    let _ = tx.try_send(p.clone());
144                }
145            }
146        });
147    }
148
149    let output = child.wait_with_output().await?;
150    if !output.status.success() {
151        let stderr = String::from_utf8_lossy(&output.stderr);
152        anyhow::bail!("ffmpeg encode failed: {stderr}");
153    }
154
155    Ok(())
156}
157
158/// Copies a segment of a video file without re-encoding.
159pub async fn extract(input: &str, output: &str, start: f64, duration: f64) -> anyhow::Result<()> {
160    if start.is_finite() && start < 0.0 {
161        anyhow::bail!("extract start must be non-negative, got {start}");
162    }
163    if !duration.is_finite() || duration <= 0.0 {
164        anyhow::bail!("extract duration must be positive, got {duration}");
165    }
166
167    let args = vec![
168        "-y".to_string(),
169        "-ss".into(),
170        format!("{start:.6}"),
171        "-i".into(),
172        input.into(),
173        "-t".into(),
174        format!("{duration:.6}"),
175        "-c".into(),
176        "copy".into(),
177        "-avoid_negative_ts".into(),
178        "make_zero".into(),
179        output.into(),
180    ];
181
182    let output = Command::new(ffmpeg_path())
183        .args(&args)
184        .stderr(std::process::Stdio::piped())
185        .output()
186        .await?;
187
188    if !output.status.success() {
189        let stderr = String::from_utf8_lossy(&output.stderr);
190        anyhow::bail!("ffmpeg extract failed: {stderr}");
191    }
192    Ok(())
193}
194
195/// Concatenates multiple encoded chunks into a single output without re-encoding.
196pub async fn concat(inputs: &[String], output: &str) -> anyhow::Result<()> {
197    if inputs.is_empty() {
198        anyhow::bail!("cannot concat an empty input list");
199    }
200
201    let list_path = make_concat_list_path(output);
202    let list_body = inputs
203        .iter()
204        .map(|path| format!("file '{}'", escape_concat_path(path)))
205        .collect::<Vec<_>>()
206        .join("\n");
207    std::fs::write(&list_path, format!("{list_body}\n"))?;
208
209    let args = vec![
210        "-y".to_string(),
211        "-f".into(),
212        "concat".into(),
213        "-safe".into(),
214        "0".into(),
215        "-i".into(),
216        list_path.to_string_lossy().into_owned(),
217        "-c".into(),
218        "copy".into(),
219        output.into(),
220    ];
221
222    let result = run_ffmpeg(args, None).await;
223    let _ = std::fs::remove_file(&list_path);
224    result
225}
226
227enum EncodePass<'a> {
228    Single,
229    First(&'a Path),
230    Second(&'a Path),
231}
232
233fn build_encode_args(job: &EncodeJob, pass: EncodePass<'_>) -> anyhow::Result<Vec<String>> {
234    let mut args = vec!["-y".into(), "-i".into(), job.input.clone(), "-an".into()];
235
236    if !matches!(pass, EncodePass::First(_)) {
237        args.extend(["-progress".into(), "pipe:1".into(), "-nostats".into()]);
238    }
239
240    args.extend(["-c:v".into(), job.codec.as_str().into()]);
241
242    // Rate control mode
243    match job.rate_control {
244        RateControlMode::Qp => match job.codec {
245            Codec::SvtAv1 => {
246                args.extend(["-qp".into(), job.crf.to_string()]);
247                args.extend(["-svtav1-params".into(), "enable-adaptive-quantization=0".into()]);
248            }
249            _ => {
250                args.extend(["-qp".into(), job.crf.to_string()]);
251            }
252        },
253        RateControlMode::CappedCrf => {
254            if job.max_bitrate <= 0.0 {
255                anyhow::bail!("max bitrate must be greater than zero for capped CRF mode");
256            }
257            let bufsize = if job.bufsize > 0.0 { job.bufsize } else { job.max_bitrate * 2.0 };
258            args.extend(["-crf".into(), job.crf.to_string()]);
259            args.extend(["-maxrate".into(), format!("{:.0}k", job.max_bitrate)]);
260            args.extend(["-bufsize".into(), format!("{bufsize:.0}k")]);
261        }
262        RateControlMode::Vbr => {
263            if job.target_bitrate <= 0.0 {
264                anyhow::bail!("target bitrate must be greater than zero for VBR mode");
265            }
266            args.extend(["-b:v".into(), format!("{:.0}k", job.target_bitrate)]);
267            args.extend(["-maxrate".into(), format!("{:.0}k", job.target_bitrate * 2.0)]);
268            args.extend(["-bufsize".into(), format!("{:.0}k", job.target_bitrate * 4.0)]);
269
270            let passlog = match pass {
271                EncodePass::First(path) => {
272                    args.extend(["-pass".into(), "1".into()]);
273                    path
274                }
275                EncodePass::Second(path) => {
276                    args.extend(["-pass".into(), "2".into()]);
277                    path
278                }
279                EncodePass::Single => {
280                    anyhow::bail!("VBR mode requires a two-pass encode flow");
281                }
282            };
283
284            args.extend(["-passlogfile".into(), passlog.to_string_lossy().into_owned()]);
285        }
286        RateControlMode::Crf => {
287            args.extend(["-crf".into(), job.crf.to_string()]);
288        }
289    }
290
291    if !job.preset.is_empty() {
292        args.extend(["-preset".into(), job.preset.clone()]);
293    }
294
295    if let Some(ref res) = job.resolution
296        && res.width > 0
297        && res.height > 0
298    {
299        args.extend(["-vf".into(), format!("scale={}:{}:flags=lanczos", res.width, res.height)]);
300    }
301
302    args.extend(job.extra_args.iter().cloned());
303
304    match pass {
305        EncodePass::First(_) => {
306            args.extend(["-f".into(), "null".into()]);
307            args.push(null_output_path().into());
308        }
309        EncodePass::Single | EncodePass::Second(_) => args.push(job.output.clone()),
310    }
311
312    Ok(args)
313}
314
315/// Escape a path for use inside single quotes in an FFmpeg concat list file.
316/// The concat demuxer treats backslash as an escape character, so both
317/// backslashes and single quotes must be escaped.
318fn escape_concat_path(path: &str) -> String {
319    path.replace('\\', "\\\\").replace('\'', "\\'")
320}
321
322fn make_passlog_prefix(output: &str) -> PathBuf {
323    let output_path = Path::new(output);
324    let parent =
325        output_path.parent().filter(|p| !p.as_os_str().is_empty()).unwrap_or(Path::new("."));
326    let stem = output_path.file_stem().and_then(|s| s.to_str()).unwrap_or("viser");
327    let unique = SystemTime::now().duration_since(UNIX_EPOCH).map(|d| d.as_millis()).unwrap_or(0);
328    parent.join(format!(".{stem}.viser-passlog-{unique}-{}", std::process::id()))
329}
330
331fn make_concat_list_path(output: &str) -> PathBuf {
332    let output_path = Path::new(output);
333    let parent =
334        output_path.parent().filter(|p| !p.as_os_str().is_empty()).unwrap_or(Path::new("."));
335    let stem = output_path.file_stem().and_then(|s| s.to_str()).unwrap_or("viser");
336    let unique = SystemTime::now().duration_since(UNIX_EPOCH).map(|d| d.as_millis()).unwrap_or(0);
337    parent.join(format!(".{stem}.viser-concat-{unique}-{}.txt", std::process::id()))
338}
339
340fn null_output_path() -> &'static str {
341    if cfg!(windows) { "NUL" } else { "/dev/null" }
342}
343
344struct PasslogCleanup {
345    parent: PathBuf,
346    prefix: String,
347}
348
349impl PasslogCleanup {
350    fn new(path: PathBuf) -> Self {
351        let parent = path.parent().unwrap_or(Path::new(".")).to_path_buf();
352        let prefix = path.file_name().and_then(|name| name.to_str()).unwrap_or_default().to_owned();
353        Self { parent, prefix }
354    }
355
356    fn run(&self) {
357        let Ok(entries) = std::fs::read_dir(&self.parent) else {
358            return;
359        };
360
361        for entry in entries.flatten() {
362            let path = entry.path();
363            let Some(name) = path.file_name().and_then(|name| name.to_str()) else {
364                continue;
365            };
366            if !name.starts_with(&self.prefix) {
367                continue;
368            }
369            if let Err(err) = std::fs::remove_file(&path) {
370                tracing::debug!(?path, ?err, "failed to remove ffmpeg two-pass log file");
371            }
372        }
373    }
374}
375
376/// Returns true when a complete progress block is ready.
377fn parse_progress_line(line: &str, p: &mut Progress) -> bool {
378    let Some((key, value)) = line.split_once('=') else {
379        return false;
380    };
381
382    match key {
383        "frame" => {
384            p.frame = value.parse().unwrap_or(0);
385        }
386        "fps" => {
387            p.fps = value.parse().unwrap_or(0.0);
388        }
389        "bitrate" => {
390            let v = value.trim_end_matches("kbits/s");
391            p.bitrate = v.parse().unwrap_or(0.0);
392        }
393        "speed" => {
394            let v = value.trim_end_matches('x');
395            p.speed = v.parse().unwrap_or(0.0);
396        }
397        "out_time_us" => {
398            let us: u64 = value.parse().unwrap_or(0);
399            p.time = Duration::from_micros(us);
400        }
401        "progress" => return true,
402        _ => {}
403    }
404    false
405}
406
407#[cfg(test)]
408mod tests {
409    use super::*;
410    use crate::Codec;
411
412    fn sample_job(mode: RateControlMode) -> EncodeJob {
413        EncodeJob {
414            input: "input.mp4".into(),
415            output: "output.mp4".into(),
416            resolution: Some(crate::Resolution::new(1280, 720)),
417            codec: Codec::X264,
418            crf: 23,
419            rate_control: mode,
420            target_bitrate: 2500.0,
421            max_bitrate: 3000.0,
422            bufsize: 6000.0,
423            preset: "medium".into(),
424            extra_args: vec![],
425        }
426    }
427
428    #[test]
429    fn test_build_encode_args_crf_single_pass() {
430        let args =
431            build_encode_args(&sample_job(RateControlMode::Crf), EncodePass::Single).unwrap();
432        assert!(args.windows(2).any(|w| w == ["-crf", "23"]));
433        assert_eq!(args.last().unwrap(), "output.mp4");
434    }
435
436    #[test]
437    fn test_build_encode_args_vbr_first_pass_uses_null_output() {
438        let job = sample_job(RateControlMode::Vbr);
439        let passlog = Path::new("/tmp/viser-passlog");
440        let args = build_encode_args(&job, EncodePass::First(passlog)).unwrap();
441        assert!(args.windows(2).any(|w| w == ["-pass", "1"]));
442        assert!(args.windows(2).any(|w| w == ["-f", "null"]));
443        assert_eq!(args.last().unwrap(), null_output_path());
444    }
445
446    #[test]
447    fn test_build_encode_args_vbr_second_pass_writes_output() {
448        let job = sample_job(RateControlMode::Vbr);
449        let passlog = Path::new("/tmp/viser-passlog");
450        let args = build_encode_args(&job, EncodePass::Second(passlog)).unwrap();
451        assert!(args.windows(2).any(|w| w == ["-pass", "2"]));
452        assert_eq!(args.last().unwrap(), "output.mp4");
453    }
454
455    #[test]
456    fn test_build_encode_args_capped_crf_sets_vbv() {
457        let args =
458            build_encode_args(&sample_job(RateControlMode::CappedCrf), EncodePass::Single).unwrap();
459        assert!(args.windows(2).any(|w| w == ["-crf", "23"]));
460        assert!(args.windows(2).any(|w| w == ["-maxrate", "3000k"]));
461        assert!(args.windows(2).any(|w| w == ["-bufsize", "6000k"]));
462    }
463}
viser_ffmpeg/encode.rs

viser_ffmpeg/
encode.rs
