ffmpeg

FFmpeg is a comprehensive open-source multimedia framework that handles video, audio, and other multimedia files and streams. It provides command-line tools and libraries for recording, converting, and streaming audio and video.

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Install skill "ffmpeg" with this command: npx skills add aia-11-hn-mib/mib-mockinterviewaibot/aia-11-hn-mib-mib-mockinterviewaibot-ffmpeg

FFmpeg Skill

FFmpeg is a comprehensive open-source multimedia framework that handles video, audio, and other multimedia files and streams. It provides command-line tools and libraries for recording, converting, and streaming audio and video.

When to Use This Skill

Use this skill when:

  • Converting media files between formats (MP4, MKV, WebM, AVI, etc.)

  • Encoding/decoding video with different codecs (H.264, H.265, VP9, AV1)

  • Processing audio files (AAC, MP3, FLAC, Opus)

  • Live streaming to platforms (Twitch, YouTube, RTMP servers)

  • Creating HLS/DASH adaptive streams

  • Extracting audio from video files

  • Applying video/audio filters (scale, crop, denoise, volume)

  • Screen recording and capture

  • Optimizing video quality and file size

  • Batch processing media files

  • Analyzing media file properties

Core Components

Command-Line Tools

ffmpeg: Primary tool for transcoding, conversion, and streaming ffprobe: Media analysis and inspection tool ffplay: Minimalist multimedia player for testing

Libraries

  • libavcodec: Encoding/decoding codecs

  • libavformat: Container formats and I/O

  • libavfilter: Audio/video filtering framework

  • libavutil: Utility functions

  • libswscale: Video scaling and color conversion

  • libswresample: Audio resampling and mixing

Common Video Codecs

Modern Codecs

H.264 (libx264): Most widely supported, excellent compression/quality balance

  • Best for: Universal compatibility, streaming, web video

  • Quality range: CRF 17-28 (lower = better quality)

H.265/HEVC (libx265): 25-50% better compression than H.264

  • Best for: 4K video, file size reduction

  • Slower encoding, limited browser support

VP9: Royalty-free, WebM format

  • Best for: YouTube, open-source projects

  • Good quality/compression, Chrome/Firefox support

AV1 (libaom-av1, libsvtav1): Next-generation codec, best compression

  • Best for: Future-proofing, ultimate quality/size ratio

  • Very slow encoding (improving with SVT-AV1)

Legacy Codecs

  • MPEG-4 (Xvid/DivX)

  • MPEG-2

  • VP8

Common Audio Codecs

AAC: Industry standard, excellent quality MP3: Universal compatibility, good quality Opus: Best quality at low bitrates, ideal for voice/streaming FLAC: Lossless compression, archival quality Vorbis: Open-source, good quality AC-3/DTS: Surround sound formats

Container Formats

MP4: Universal compatibility, streaming-friendly MKV (Matroska): Feature-rich, supports multiple tracks/subtitles WebM: Web-optimized (VP8/VP9 + Vorbis/Opus) AVI: Legacy format, broad compatibility MOV: Apple QuickTime format TS: Transport stream for broadcasting FLV: Flash video (legacy streaming)

Basic Operations

Format Conversion

Simple format conversion without re-encoding:

ffmpeg -i input.mkv -c copy output.mp4

Convert with specific codecs:

ffmpeg -i input.avi -c:v libx264 -c:a aac output.mp4

Quality-Based Encoding (CRF)

Constant Rate Factor - best for quality-focused encoding:

H.264 encoding (CRF 23 = default, 17-28 recommended range)

ffmpeg -i input.mkv -c:v libx264 -preset slow -crf 22 -c:a copy output.mp4

H.265 encoding (higher compression)

ffmpeg -i input.mkv -c:v libx265 -preset medium -crf 24 -c:a copy output.mp4

VP9 encoding (WebM)

ffmpeg -i input.mkv -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus output.webm

CRF Scale:

  • 0 = Lossless (huge file size)

  • 17-18 = Visually lossless

  • 20-23 = High quality (recommended)

  • 24-28 = Medium quality

  • 30+ = Low quality

  • 51 = Worst quality

Presets (speed vs compression):

  • ultrafast, superfast, veryfast, faster, fast

  • medium (default)

  • slow, slower, veryslow (better compression)

  • placebo (not recommended - minimal gains)

Bitrate-Based Encoding (Two-Pass)

For targeting specific file sizes:

Pass 1 (analysis)

ffmpeg -y -i input.mkv -c:v libx264 -b:v 2600k -pass 1 -an -f null /dev/null

Pass 2 (encoding)

ffmpeg -i input.mkv -c:v libx264 -b:v 2600k -pass 2 -c:a aac -b:a 128k output.mp4

Audio Extraction

Extract audio without re-encoding:

ffmpeg -i video.mp4 -vn -c:a copy audio.m4a

Extract and convert to MP3:

ffmpeg -i video.mp4 -vn -q:a 0 audio.mp3

Extract with specific bitrate:

ffmpeg -i video.mp4 -vn -c:a libmp3lame -b:a 192k audio.mp3

Video Scaling/Resizing

Scale to specific dimensions:

ffmpeg -i input.mp4 -vf scale=1280:720 output.mp4

Scale maintaining aspect ratio:

Width 1280, height auto-calculated

ffmpeg -i input.mp4 -vf scale=1280:-1 output.mp4

Height 720, width auto-calculated

ffmpeg -i input.mp4 -vf scale=-1:720 output.mp4

Scale to half resolution:

ffmpeg -i input.mp4 -vf scale=iw/2:ih/2 output.mp4

Trimming/Cutting Video

Cut without re-encoding (fast but less precise):

ffmpeg -i input.mp4 -ss 00:01:30 -to 00:03:00 -c copy output.mp4

Cut with re-encoding (precise):

ffmpeg -i input.mp4 -ss 00:01:30 -t 00:01:30 -c:v libx264 -c:a aac output.mp4

Parameters:

  • -ss : Start time (HH:MM:SS or seconds)

  • -to : End time

  • -t : Duration (instead of end time)

Concatenation

Method 1: Concat demuxer (same codec/format)

Create concat.txt :

file 'input1.mp4' file 'input2.mp4' file 'input3.mp4'

Run:

ffmpeg -f concat -safe 0 -i concat.txt -c copy output.mp4

Method 2: Concat filter (different formats)

ffmpeg -i input1.mp4 -i input2.mp4 -i input3.mp4
-filter_complex "[0:v][0:a][1:v][1:a][2:v][2:a]concat=n=3:v=1:a=1[v][a]"
-map "[v]" -map "[a]" output.mp4

Advanced Filtering

Video Filters

Multiple filters (chain with comma):

ffmpeg -i input.mp4 -vf "scale=1280:720,hqdn3d" output.mp4

Denoise:

ffmpeg -i input.mp4 -vf hqdn3d output.mp4

Deinterlace:

ffmpeg -i input.mp4 -vf yadif output.mp4

Crop:

Crop to 1280x720 from top-left (0,0)

ffmpeg -i input.mp4 -vf "crop=1280:720:0:0" output.mp4

Auto-detect and remove black borders

ffmpeg -i input.mp4 -vf "cropdetect" output.mp4

Rotate:

Rotate 90 degrees clockwise

ffmpeg -i input.mp4 -vf "transpose=1" output.mp4

Rotate 180 degrees

ffmpeg -i input.mp4 -vf "transpose=1,transpose=1" output.mp4

Watermark/Logo:

ffmpeg -i video.mp4 -i logo.png
-filter_complex "overlay=10:10" output.mp4

Speed adjustment:

2x speed

ffmpeg -i input.mp4 -vf "setpts=0.5*PTS" -af "atempo=2.0" output.mp4

0.5x speed (slow motion)

ffmpeg -i input.mp4 -vf "setpts=2.0*PTS" -af "atempo=0.5" output.mp4

Audio Filters

Volume adjustment:

Increase volume by 10dB

ffmpeg -i input.mp4 -af "volume=10dB" output.mp4

Set to 50% volume

ffmpeg -i input.mp4 -af "volume=0.5" output.mp4

Normalize audio:

ffmpeg -i input.mp4 -af loudnorm output.mp4

Crossfade between audio:

ffmpeg -i audio1.mp3 -i audio2.mp3
-filter_complex "[0][1]acrossfade=d=5" output.mp3

Mix multiple audio tracks:

ffmpeg -i input1.mp3 -i input2.mp3
-filter_complex "[0:a][1:a]amix=inputs=2:duration=longest" output.mp3

Streaming

RTMP Streaming (Twitch/YouTube)

Basic stream:

ffmpeg -re -i input.mp4 -c:v libx264 -preset veryfast
-maxrate 3000k -bufsize 6000k -pix_fmt yuv420p -g 50
-c:a aac -b:a 128k -ar 44100
-f flv rtmp://live.twitch.tv/app/YOUR_STREAM_KEY

Screen capture + stream (Linux):

ffmpeg -f x11grab -s 1920x1080 -framerate 30 -i :0.0
-f pulse -ac 2 -i default
-c:v libx264 -preset veryfast -tune zerolatency
-maxrate 2500k -bufsize 5000k -pix_fmt yuv420p
-c:a aac -b:a 128k -ar 44100
-f flv rtmp://live.twitch.tv/app/YOUR_STREAM_KEY

Screen capture (Windows DirectShow):

ffmpeg -f dshow -i video="screen-capture-recorder":audio="Stereo Mix"
-c:v libx264 -preset ultrafast -tune zerolatency
-maxrate 750k -bufsize 3000k
-f flv rtmp://live.twitch.tv/app/YOUR_STREAM_KEY

Important streaming parameters:

  • -re : Read input at native frame rate (real-time)

  • -tune zerolatency : Optimize for low latency

  • -g 50 : Keyframe every 50 frames (2 seconds @ 25fps)

  • -maxrate : Maximum bitrate

  • -bufsize : Rate control buffer (typically 2x maxrate)

HLS Streaming

Generate adaptive HLS stream:

ffmpeg -i input.mp4
-c:v libx264 -preset fast -crf 22 -g 48 -sc_threshold 0
-c:a aac -b:a 128k
-f hls -hls_time 6 -hls_playlist_type vod
-hls_segment_filename "segment_%03d.ts"
playlist.m3u8

Multi-bitrate HLS:

ffmpeg -i input.mp4
-map 0:v -map 0:a -map 0:v -map 0:a
-c:v libx264 -crf 22 -c:a aac -b:a 128k
-b:v:0 2000k -s:v:0 1280x720 -b:v:1 5000k -s:v:1 1920x1080
-var_stream_map "v:0,a:0 v:1,a:1"
-master_pl_name master.m3u8
-f hls -hls_time 6 -hls_list_size 0
stream_%v/index.m3u8

UDP/RTP Streaming

UDP stream:

ffmpeg -re -i input.mp4 -c copy -f mpegts udp://192.168.1.100:1234

RTP audio stream:

ffmpeg -re -i audio.mp3 -c:a libopus -f rtp rtp://192.168.1.100:5004

Hardware Acceleration

NVIDIA NVENC

H.264 with NVENC

ffmpeg -hwaccel cuda -i input.mp4 -c:v h264_nvenc -preset fast -crf 22 output.mp4

H.265 with NVENC

ffmpeg -hwaccel cuda -i input.mp4 -c:v hevc_nvenc -preset fast -crf 24 output.mp4

Intel QuickSync (QSV)

ffmpeg -hwaccel qsv -c:v h264_qsv -i input.mp4
-c:v h264_qsv -preset fast -global_quality 22 output.mp4

AMD VCE

ffmpeg -hwaccel auto -i input.mp4
-c:v h264_amf -quality balanced -rc cqp -qp 22 output.mp4

Media Analysis

Inspect media file

Detailed information

ffprobe -v quiet -print_format json -show_format -show_streams input.mp4

Human-readable format

ffprobe input.mp4

Get duration

ffprobe -v error -show_entries format=duration
-of default=noprint_wrappers=1:nokey=1 input.mp4

Get resolution

ffprobe -v error -select_streams v:0
-show_entries stream=width,height
-of csv=s=x:p=0 input.mp4

Get bitrate

ffprobe -v error -show_entries format=bit_rate
-of default=noprint_wrappers=1:nokey=1 input.mp4

Batch Processing

Bash loop for batch conversion

Convert all MKV files to MP4

for file in *.mkv; do ffmpeg -i "$file" -c:v libx264 -crf 22 -c:a aac "${file%.mkv}.mp4" done

Resize all videos to 720p

for file in *.mp4; do ffmpeg -i "$file" -vf scale=-1:720 "720p_${file}" done

Parallel processing with GNU Parallel

Install: sudo apt-get install parallel

Process multiple files in parallel

ls *.mkv | parallel ffmpeg -i {} -c:v libx264 -crf 22 -c:a aac {.}.mp4

Common Patterns

Create GIF from video

High quality GIF

ffmpeg -i input.mp4 -vf "fps=15,scale=640:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" output.gif

Simple GIF

ffmpeg -i input.mp4 -vf "fps=10,scale=320:-1" output.gif

Extract frames as images

Extract all frames

ffmpeg -i input.mp4 frame_%04d.png

Extract 1 frame per second

ffmpeg -i input.mp4 -vf fps=1 frame_%04d.png

Extract single frame at 5 seconds

ffmpeg -ss 00:00:05 -i input.mp4 -frames:v 1 frame.png

Create video from images

From numbered images

ffmpeg -framerate 30 -i frame_%04d.png -c:v libx264 -crf 22 -pix_fmt yuv420p output.mp4

From pattern

ffmpeg -framerate 24 -pattern_type glob -i '*.png' -c:v libx264 output.mp4

Add subtitles

Burn subtitles into video

ffmpeg -i video.mp4 -vf subtitles=subtitles.srt output.mp4

Embed subtitle track (soft subtitles)

ffmpeg -i video.mp4 -i subtitles.srt -c copy -c:s mov_text output.mp4

Remove audio

ffmpeg -i input.mp4 -an -c:v copy output.mp4

Replace audio

ffmpeg -i video.mp4 -i audio.mp3 -c:v copy -c:a aac -map 0:v:0 -map 1:a:0 output.mp4

Create thumbnail

Single thumbnail at 5 seconds

ffmpeg -i input.mp4 -ss 00:00:05 -vframes 1 -vf scale=320:-1 thumb.jpg

Multiple thumbnails (one per minute)

ffmpeg -i input.mp4 -vf fps=1/60,scale=320:-1 thumb_%03d.jpg

Performance Optimization

Speed vs Quality Trade-offs

Fast encoding (real-time processing):

ffmpeg -i input.mp4 -c:v libx264 -preset ultrafast -crf 23 output.mp4

Balanced (default):

ffmpeg -i input.mp4 -c:v libx264 -preset medium -crf 22 output.mp4

High quality (archival):

ffmpeg -i input.mp4 -c:v libx264 -preset veryslow -crf 18 output.mp4

Multi-threading

FFmpeg automatically uses multiple CPU cores. Override with:

ffmpeg -threads 8 -i input.mp4 -c:v libx264 output.mp4

Best Practices

  • Use CRF for quality-focused encoding - Better than bitrate for most use cases

  • Two-pass for size targets - When file size is critical

  • Copy streams when possible - Use -c copy to avoid re-encoding

  • Choose appropriate presets - Balance speed vs compression

  • Match output to source - Don't upscale or use higher quality than source

  • Test short clips first - Verify settings before batch processing

  • Hardware acceleration - Use GPU encoding for faster processing

  • Audio matters - Don't neglect audio codec/bitrate choices

  • Use filters efficiently - Chain multiple filters with commas

  • Verify output - Always check quality after encoding

Common Parameters Reference

Video Parameters

  • -c:v or -vcodec : Video codec

  • -b:v : Video bitrate (e.g., 2M , 2500k )

  • -crf : Constant Rate Factor (0-51)

  • -preset : Encoding speed/quality (ultrafast to veryslow)

  • -tune : Encoding optimization (film, animation, zerolatency)

  • -pix_fmt : Pixel format (yuv420p for compatibility)

  • -r : Frame rate (e.g., 30 , 60 )

  • -g : GOP size (keyframe interval)

Audio Parameters

  • -c:a or -acodec : Audio codec

  • -b:a : Audio bitrate (e.g., 128k , 192k )

  • -ar : Audio sample rate (e.g., 44100 , 48000 )

  • -ac : Audio channels (1=mono, 2=stereo)

  • -q:a : Audio quality for VBR (0=best for MP3)

General Parameters

  • -i : Input file

  • -y : Overwrite output without asking

  • -n : Never overwrite output

  • -t : Duration to encode

  • -ss : Start time offset

  • -to : End time

  • -vf : Video filters

  • -af : Audio filters

  • -map : Stream selection

  • -metadata : Set metadata

  • -f : Force format

Troubleshooting

"Unknown encoder" errors

Install codec libraries:

Ubuntu/Debian

sudo apt-get install ffmpeg libx264-dev libx265-dev libvpx-dev

Check available encoders

ffmpeg -encoders

Output compatibility issues

Use safe defaults for maximum compatibility:

ffmpeg -i input.mkv -c:v libx264 -profile:v high -level 4.0
-pix_fmt yuv420p -c:a aac -b:a 128k output.mp4

Performance issues

  • Use hardware acceleration (-hwaccel )

  • Choose faster presets (-preset fast )

  • Reduce resolution with scale filter

  • Use multiple threads explicitly

Quality issues

  • Lower CRF value (18-22 for high quality)

  • Use slower preset (-preset slow )

  • Use two-pass encoding for better bitrate distribution

  • Match or exceed source bitrate

Resources

Implementation Checklist

When using FFmpeg:

  • Verify FFmpeg installation (ffmpeg -version )

  • Check available codecs for your use case

  • Test encoding settings on short clip first

  • Choose appropriate codec for target platform

  • Set quality level (CRF or bitrate)

  • Configure audio codec and bitrate

  • Apply necessary filters (scale, crop, etc.)

  • Consider hardware acceleration if available

  • Verify output quality and file size

  • Test output compatibility on target devices

  • Document settings for reproducibility

  • Create batch scripts for repetitive tasks

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