Speed

Speed up or slow down a video or its sound; the sound keeps its pitch.

speed changes how fast a video plays, picture and sound, from 0.25 to 4 times. An audio output takes it too. The sound keeps its pitch.

The request#

bash

curl "$VIDEXO_API_URL/v1/transcode" \
  -H "Authorization: Bearer $VIDEXO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "input": "https://example.com/talk.mp4",
  "filename": "talk-2x.mp4",
  "speed": 2
}'

JavaScript

const response = await fetch(`${process.env.VIDEXO_API_URL}/v1/transcode`, {
  method: 'POST',
  headers: {
    Authorization: `Bearer ${process.env.VIDEXO_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "input": "https://example.com/talk.mp4",
    "filename": "talk-2x.mp4",
    "speed": 2
  }),
});
const job = await response.json();

bash

ffmpeg \
  -i https://example.com/talk.mp4 \
  -map 0:v:0 \
  -vf "scale='min(trunc(iw/2)*2,min(7680,min(trunc(7680*iw/ih/2)*2,trunc(sqrt(33554432*iw/ih)/2)*2)))':-2,setpts=PTS/2" \
  -c:v libx264 -preset veryfast -crf 23 -pix_fmt yuv420p \
  -map "0:a:0?" \
  -af atempo=2 \
  -c:a aac -b:a 128k -movflags +faststart \
  talk-2x.mp4

talk-2x.mp4: picture and sound at twice the speed, the sound at its own pitch.

Sound mixed in with audio.mix stays at its own speed, and a stream copy ("codec": "copy") cannot change speed. For a picture without sound, set "audio": false.

Slow motion#

bash

curl "$VIDEXO_API_URL/v1/transcode" \
  -H "Authorization: Bearer $VIDEXO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "input": "https://example.com/talk.mp4",
  "filename": "talk-slow.mp4",
  "trim": {
    "start": 42,
    "duration": 5
  },
  "speed": 0.5
}'

JavaScript

const response = await fetch(`${process.env.VIDEXO_API_URL}/v1/transcode`, {
  method: 'POST',
  headers: {
    Authorization: `Bearer ${process.env.VIDEXO_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "input": "https://example.com/talk.mp4",
    "filename": "talk-slow.mp4",
    "trim": {
      "start": 42,
      "duration": 5
    },
    "speed": 0.5
  }),
});
const job = await response.json();

bash

ffmpeg \
  -ss 42 -t 5 -i https://example.com/talk.mp4 \
  -map 0:v:0 \
  -vf "scale='min(trunc(iw/2)*2,min(7680,min(trunc(7680*iw/ih/2)*2,trunc(sqrt(33554432*iw/ih)/2)*2)))':-2,setpts=PTS/0.5" \
  -c:v libx264 -preset veryfast -crf 23 -pix_fmt yuv420p \
  -map "0:a:0?" \
  -af atempo=0.5 \
  -c:a aac -b:a 128k -movflags +faststart \
  talk-slow.mp4

GIFs take speed too, for a time-lapse preview.