ffmpeg

Name: ffmpeg
Author: calesthio

337installs4.9kforks

How to install ffmpeg?

calesthio/openmontage/ffmpeg

$npx -y skills add calesthio/OpenMontage --skill ffmpeg

Installs into the current project.

Summary

Video and audio processing with FFmpeg. Use for format conversion, resizing, compression, audio extraction, and preparing assets for Remotion. Triggers include converting GIF to MP4, resizing video, extracting audio, compressing files, or any media transformation task.

Files · 1

View on GitHub

SKILL.md

1	# FFmpeg for Video Production
2
3	FFmpeg is the essential tool for video/audio processing. This skill covers common operations for Remotion video projects.
4
5	## Quick Reference
6
7	### GIF to MP4 (Remotion-compatible)
8
9	```bash
10	ffmpeg -i input.gif -movflags faststart -pix_fmt yuv420p \
11	-vf "scale=trunc(iw/2)2:trunc(ih/2)2" output.mp4
12	```
13
14	Why these flags:
15	- `-movflags faststart` - Moves metadata to start for web streaming
16	- `-pix_fmt yuv420p` - Ensures compatibility with most players
17	- `scale=trunc(...)` - Forces even dimensions (required by most codecs)
18
19	### Resize Video
20
21	```bash
22	# To 1920x1080 (maintain aspect ratio, add black bars)
23	ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2" output.mp4
24
25	# To 1920x1080 (crop to fill)
26	ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=increase,crop=1920:1080" output.mp4
27
28	# Scale to width, auto height
29	ffmpeg -i input.mp4 -vf "scale=1280:-2" output.mp4
30	```
31
32	### Compress Video
33
34	```bash
35	# Good quality, smaller file (CRF 23 is default, lower = better quality)
36	ffmpeg -i input.mp4 -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k output.mp4
37
38	# Aggressive compression for web preview
39	ffmpeg -i input.mp4 -c:v libx264 -crf 28 -preset fast -c:a aac -b:a 96k output.mp4
40
41	# Target file size (e.g., ~10MB for 60s video = ~1.3Mbps)
42	ffmpeg -i input.mp4 -c:v libx264 -b:v 1300k -c:a aac -b:a 128k output.mp4
43	```
44
45	### Extract Audio
46
47	```bash
48	# Extract to MP3
49	ffmpeg -i input.mp4 -vn -acodec libmp3lame -q:a 2 output.mp3
50
51	# Extract to AAC
52	ffmpeg -i input.mp4 -vn -acodec aac -b:a 192k output.m4a
53
54	# Extract to WAV (uncompressed)
55	ffmpeg -i input.mp4 -vn output.wav
56	```
57
58	### Convert Audio Formats
59
60	```bash
61	# M4A to MP3 (for ElevenLabs voice samples)
62	ffmpeg -i input.m4a -codec:a libmp3lame -qscale:a 2 output.mp3
63
64	# WAV to MP3
65	ffmpeg -i input.wav -codec:a libmp3lame -b:a 192k output.mp3
66
67	# Adjust volume
68	ffmpeg -i input.mp3 -filter:a "volume=1.5" output.mp3
69	```
70
71	### Trim/Cut Video
72
73	```bash
74	# Cut from timestamp to duration (recommended - reliable)
75	ffmpeg -i input.mp4 -ss 00:00:30 -t 00:00:15 -c:v libx264 -c:a aac output.mp4
76
77	# Cut from timestamp to timestamp
78	ffmpeg -i input.mp4 -ss 00:00:30 -to 00:00:45 -c:v libx264 -c:a aac output.mp4
79
80	# Stream copy (faster but may lose frames at cut points)
81	# Only use when source has frequent keyframes
82	ffmpeg -i input.mp4 -ss 00:00:30 -t 00:00:15 -c copy output.mp4
83	```
84
85	Note: Re-encoding is recommended for trimming. Stream copy (`-c copy`) can silently drop video if the seek point doesn't align with a keyframe.
86
87	### Speed Up / Slow Down
88
89	```bash
90	# 2x speed (video and audio)
91	ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mp4
92
93	# 0.5x speed (slow motion)
94	ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=2.0*PTS[v];[0:a]atempo=0.5[a]" -map "[v]" -map "[a]" output.mp4
95
96	# Video only (no audio)
97	ffmpeg -i input.mp4 -filter:v "setpts=0.5*PTS" -an output.mp4
98	```
99
100	### Concatenate Videos
101
102	```bash
103	# Create file list
104	echo "file 'clip1.mp4'" > list.txt
105	echo "file 'clip2.mp4'" >> list.txt
106	echo "file 'clip3.mp4'" >> list.txt
107
108	# Concatenate (same codec/resolution)
109	ffmpeg -f concat -safe 0 -i list.txt -c copy output.mp4
110
111	# Concatenate with re-encoding (different sources)
112	ffmpeg -f concat -safe 0 -i list.txt -c:v libx264 -c:a aac output.mp4
113	```
114
115	### Add Fade In/Out
116
117	```bash
118	# Fade in first 1 second, fade out last 1 second (30fps video)
119	ffmpeg -i input.mp4 -vf "fade=t=in:st=0:d=1,fade=t=out:st=9:d=1" -c:a copy output.mp4
120
121	# Audio fade
122	ffmpeg -i input.mp4 -af "afade=t=in:st=0:d=1,afade=t=out:st=9:d=1" -c:v copy output.mp4
123	```
124
125	### Get Video Info
126
127	```bash
128	# Duration, resolution, codec info
129	ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 input.mp4
130
131	# Full info
132	ffprobe -v quiet -print_format json -show_format -show_streams input.mp4
133	```
134
135	## Remotion-Specific Patterns
136
137	### Video Speed Adjustment for Remotion
138
139	When to use FFmpeg vs Remotion `playbackRate`:
140
141	\| Scenario \| Use FFmpeg \| Use Remotion \|
142	\|----------\|------------\|--------------\|
143	\| Constant speed (1.5x, 2x) \| Either works \| ✅ Simpler \|
144	\| Extreme speeds (>4x or <0.25x) \| ✅ More reliable \| May have issues \|
145	\| Variable speed (accelerate over time) \| ✅ Pre-process \| Complex workaround needed \|
146	\| Need perfect audio sync \| ✅ Guaranteed \| Usually fine \|
147	\| Demo needs to fit voiceover timing \| ✅ Pre-calculate \| Runtime adjustment \|
148
149	Remotion limitation: `playbackRate` must be constant. Dynamic interpolation like `playbackRate={interpolate(frame, [0, 100], [1, 5])}` won't work correctly because Remotion evaluates frames independently.
150
151	```bash
152	# Speed up

People who liked this also viewed

6 picks

Type

ffmpeg

337installs4.9kforks

View on GitHub

How to install ffmpeg?

calesthio/openmontage/ffmpeg

$npx -y skills add calesthio/OpenMontage --skill ffmpeg

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# FFmpeg for Video Production
2
3	FFmpeg is the essential tool for video/audio processing. This skill covers common operations for Remotion video projects.
4
5	## Quick Reference
6
7	### GIF to MP4 (Remotion-compatible)
8
9	```bash
10	ffmpeg -i input.gif -movflags faststart -pix_fmt yuv420p \
11	-vf "scale=trunc(iw/2)2:trunc(ih/2)2" output.mp4
12	```
13
14	Why these flags:
15	- `-movflags faststart` - Moves metadata to start for web streaming
16	- `-pix_fmt yuv420p` - Ensures compatibility with most players
17	- `scale=trunc(...)` - Forces even dimensions (required by most codecs)
18
19	### Resize Video
20
21	```bash
22	# To 1920x1080 (maintain aspect ratio, add black bars)
23	ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2" output.mp4
24
25	# To 1920x1080 (crop to fill)
26	ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=increase,crop=1920:1080" output.mp4
27
28	# Scale to width, auto height
29	ffmpeg -i input.mp4 -vf "scale=1280:-2" output.mp4
30	```
31
32	### Compress Video
33
34	```bash
35	# Good quality, smaller file (CRF 23 is default, lower = better quality)
36	ffmpeg -i input.mp4 -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k output.mp4
37
38	# Aggressive compression for web preview
39	ffmpeg -i input.mp4 -c:v libx264 -crf 28 -preset fast -c:a aac -b:a 96k output.mp4
40
41	# Target file size (e.g., ~10MB for 60s video = ~1.3Mbps)
42	ffmpeg -i input.mp4 -c:v libx264 -b:v 1300k -c:a aac -b:a 128k output.mp4
43	```
44
45	### Extract Audio
46
47	```bash
48	# Extract to MP3
49	ffmpeg -i input.mp4 -vn -acodec libmp3lame -q:a 2 output.mp3
50
51	# Extract to AAC
52	ffmpeg -i input.mp4 -vn -acodec aac -b:a 192k output.m4a
53
54	# Extract to WAV (uncompressed)
55	ffmpeg -i input.mp4 -vn output.wav
56	```
57
58	### Convert Audio Formats
59
60	```bash
61	# M4A to MP3 (for ElevenLabs voice samples)
62	ffmpeg -i input.m4a -codec:a libmp3lame -qscale:a 2 output.mp3
63
64	# WAV to MP3
65	ffmpeg -i input.wav -codec:a libmp3lame -b:a 192k output.mp3
66
67	# Adjust volume
68	ffmpeg -i input.mp3 -filter:a "volume=1.5" output.mp3
69	```
70
71	### Trim/Cut Video
72
73	```bash
74	# Cut from timestamp to duration (recommended - reliable)
75	ffmpeg -i input.mp4 -ss 00:00:30 -t 00:00:15 -c:v libx264 -c:a aac output.mp4
76
77	# Cut from timestamp to timestamp
78	ffmpeg -i input.mp4 -ss 00:00:30 -to 00:00:45 -c:v libx264 -c:a aac output.mp4
79
80	# Stream copy (faster but may lose frames at cut points)
81	# Only use when source has frequent keyframes
82	ffmpeg -i input.mp4 -ss 00:00:30 -t 00:00:15 -c copy output.mp4
83	```
84
85	Note: Re-encoding is recommended for trimming. Stream copy (`-c copy`) can silently drop video if the seek point doesn't align with a keyframe.
86
87	### Speed Up / Slow Down
88
89	```bash
90	# 2x speed (video and audio)
91	ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mp4
92
93	# 0.5x speed (slow motion)
94	ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=2.0*PTS[v];[0:a]atempo=0.5[a]" -map "[v]" -map "[a]" output.mp4
95
96	# Video only (no audio)
97	ffmpeg -i input.mp4 -filter:v "setpts=0.5*PTS" -an output.mp4
98	```
99
100	### Concatenate Videos
101
102	```bash
103	# Create file list
104	echo "file 'clip1.mp4'" > list.txt
105	echo "file 'clip2.mp4'" >> list.txt
106	echo "file 'clip3.mp4'" >> list.txt
107
108	# Concatenate (same codec/resolution)
109	ffmpeg -f concat -safe 0 -i list.txt -c copy output.mp4
110
111	# Concatenate with re-encoding (different sources)
112	ffmpeg -f concat -safe 0 -i list.txt -c:v libx264 -c:a aac output.mp4
113	```
114
115	### Add Fade In/Out
116
117	```bash
118	# Fade in first 1 second, fade out last 1 second (30fps video)
119	ffmpeg -i input.mp4 -vf "fade=t=in:st=0:d=1,fade=t=out:st=9:d=1" -c:a copy output.mp4
120
121	# Audio fade
122	ffmpeg -i input.mp4 -af "afade=t=in:st=0:d=1,afade=t=out:st=9:d=1" -c:v copy output.mp4
123	```
124
125	### Get Video Info
126
127	```bash
128	# Duration, resolution, codec info
129	ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 input.mp4
130
131	# Full info
132	ffprobe -v quiet -print_format json -show_format -show_streams input.mp4
133	```
134
135	## Remotion-Specific Patterns
136
137	### Video Speed Adjustment for Remotion
138
139	When to use FFmpeg vs Remotion `playbackRate`:
140
141	\| Scenario \| Use FFmpeg \| Use Remotion \|
142	\|----------\|------------\|--------------\|
143	\| Constant speed (1.5x, 2x) \| Either works \| ✅ Simpler \|
144	\| Extreme speeds (>4x or <0.25x) \| ✅ More reliable \| May have issues \|
145	\| Variable speed (accelerate over time) \| ✅ Pre-process \| Complex workaround needed \|
146	\| Need perfect audio sync \| ✅ Guaranteed \| Usually fine \|
147	\| Demo needs to fit voiceover timing \| ✅ Pre-calculate \| Runtime adjustment \|
148
149	Remotion limitation: `playbackRate` must be constant. Dynamic interpolation like `playbackRate={interpolate(frame, [0, 100], [1, 5])}` won't work correctly because Remotion evaluates frames independently.
150
151	```bash
152	# Speed up

People who liked this also viewed

6 picks

Type