Using FFmpeg for converting videos to H.264
H.264 video codec and AAC audio codec offers good compression and quality balance. Using this terminal command template and replacing the input_video.ext and output_video.ext we can convert the video.
ffmpeg -i input_video.ext -c:v libx264 -preset slow -crf 23 -c:a aac -b:a 128k -vf "scale=-1:480" -movflags +faststart output_video.mp4Explanation
-i input_video.ext: Specifies the input video file.
-c:v libx264: Sets the video codec to H.264.
-preset slow: Adjusts the encoding speed and compression ratio. Options include: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow. A slower preset provides better compression but takes more time to encode.
-crf 23: Sets the Constant Rate Factor (CRF) value for the video quality. A lower value provides better quality but larger file size. Values range from 0 (lossless) to 51 (lowest quality). Recommended values are between 18 and 28.
-c:a aac: Sets the audio codec to AAC.
-b:a 128k: Sets the audio bitrate to 128 kbps.
-vf "scale=-1:480": Scales the video to a height of 480 pixels while maintaining the aspect ratio. You can adjust the value to control the output video resolution.
-movflags +faststart: Moves metadata to the beginning of the file for faster streaming.
Combining videos
Create a text file that lists the input video files in the following format (one file per line).
file 'video1.mp4'
file 'video2.mp4'Replace the input_files.txt and output_video.mp4. Use the following command template:
ffmpeg -f concat -safe 0 -i input_files.txt -c copy output_video.mp4Explanation
-f concat: Specifies the concat demuxer format to concatenate the files.
-safe 0: Allows usage of absolute file paths and disables the safe mode for the concat demuxer. Set it to 1 if you are using relative paths in the text file.
-i input_files.txt: Specifies the input text file containing the list of video files.
-c copy: Copies the streams (video, audio, and others) from the input files without re-encoding them.
Watermarking Videos
This command first scales the watermark to 20% of the video height while maintaining its aspect ratio, then overlays the scaled watermark to the bottom right corner of the video.
ffmpeg -i input.mp4 -i watermark.png -filter_complex "[1][0]scale2ref=oh*mdar:ih*0.2[logo][video];[video][logo]overlay=W-w-10:H-h-10" output_scaled.mp4Explanation
[1][0]: These are input stream specifiers. In FFmpeg, [0] generally refers to the first input file, and [1] to the second input file. In your command, [0] refers to input.mp4 and [1] refers to watermark.png.
scale2ref: This is a filter that scales the second input to match the reference. In this case, it scales the watermark (second input) to match the video (first input).
=oh*mdar:ih*0.2: These are the options for the scale2ref filter.
oh*mdar: This scales the width of the watermark. oh refers to the original height of the first input (the video), and mdar (main display aspect ratio) is the aspect ratio of the first input. This ensures that the watermark retains its original aspect ratio when scaled.
ih*0.2: This scales the height of the watermark to 20% of the height of the video. ih refers to the input height of the first input (the video).
[logo][video]: These are output labels. The scaled watermark is labeled as logo, and the unscaled video is labeled as video. These labels are used later in the command to refer to these specific streams.
W-w-10:H-h-10 positions the watermark 10 pixels from the bottom right corner of the video. You can adjust the 10 value to increase or decrease the margin.
W and H represent the width and height of the video.
w and h represent the width and height of the watermark.