Transparent image + audio to transparent video

This FFmpeg command converts an image and audio into a WebM video.
This command is optimized for creating a web-friendly video that combines a static image with audio, prioritizing fast encoding speed over maximum quality.

Input Options

• -loop 1: Loops the image continuously (makes a static image last for the duration of the audio)
• -i image.png: First input - the static image
• -i audio.mp3: Second input - the audio file

Audio Encoding Options

• -c:a libvorbis: Use Vorbis codec for audio
• -b:a 128k: Set audio bitrate to 128 kbps

Video Encoding Options

• -c:v libvpx-vp9: Use VP9 codec for video
• -tune psnr: Optimize for PSNR (Peak Signal-to-Noise Ratio) quality metrics
• -g 7500: Set keyframe interval to 7500 frames
• -keyint_min 7500: Set minimum keyframe interval also to 7500 frames
• -crf 40: Set Constant Rate Factor to 40 (higher value means lower quality but smaller file size)
• -pix_fmt yuva420p: Use YUV420P pixel format with alpha channel
• -threads 4: Use 4 CPU threads for encoding
• -speed 5: Set encoding speed (higher value is faster but lower quality)
• -deadline realtime: Use realtime encoding mode (faster but lower quality)

Output Options

• -shortest: End the video when the shortest input ends (likely the audio in this case)
• -movflags +frag_keyframe+empty_moov: Optimize for web playback
• -f webm: Force WebM container format
• output.webm: Output filename