When it comes to encoding video files, the choice of codec can greatly influence both the quality and the size of the output file. One popular choice among video editors and content creators is the HEVC codec, also known as H.265 or X265. This codec is known for its ability to compress video files to a smaller size while maintaining high-quality visuals. However, one common question arises: What is the ideal size to encode X265 by FFmpeg?
Original Code
Below is a sample command that you might use to encode a video file with X265 using FFmpeg:
ffmpeg -i input.mp4 -c:v libx265 -preset medium -crf 28 output.mp4
Breaking Down the Command:
-i input.mp4: This specifies the input video file you want to encode.-c:v libx265: This indicates that you are using the X265 codec for video encoding.-preset medium: This option allows you to balance the encoding speed and file size. Options vary fromultrafasttoveryslow.-crf 28: The Constant Rate Factor (CRF) controls the output quality. A lower value yields better quality (and larger files), while a higher value results in lower quality (and smaller files).output.mp4: This is the name of the output file.
Ideal File Size Considerations
Determining the ideal size for an X265 encoded video involves various factors such as target audience, playback devices, and the nature of the content. Here are key points to consider:
1. Purpose of the Video:
- For Streaming: If the video is intended for streaming platforms, a balance between quality and size is crucial. Typically, a size of around 1 GB for a one-hour video at 1080p resolution is a good target.
- For Archival: If the video is for archival purposes, maintaining higher quality (resulting in larger files) may be important. In this case, aiming for a size of 1.5-2 GB per hour can be ideal.
2. Resolution and Frame Rate:
- Higher resolutions such as 4K will result in larger files even with X265's compression efficiency. For 4K video, a size between 15-30 GB for a one-hour video is typical, depending on the content complexity and motion.
3. Quality Settings:
- The CRF setting plays a pivotal role in determining file size. For typical uses:
- CRF 23-28: A sweet spot for general usage, balancing size and quality for most applications.
- CRF 18-22: Optimal for high-quality outputs, suitable for content that demands excellent visual fidelity.
Practical Examples
Here are a few practical examples of encoding settings:
Example 1: General Purpose (1080p)
ffmpeg -i input.mp4 -c:v libx265 -preset medium -crf 24 output.mp4
This configuration would generally produce a quality output suitable for YouTube or home use, balancing quality and file size.
Example 2: High Quality (4K)
ffmpeg -i input.mp4 -c:v libx265 -preset slow -crf 20 output.mp4
This configuration is ideal for archiving or displaying on large screens, where quality is paramount.
Example 3: Streaming (720p)
ffmpeg -i input.mp4 -c:v libx265 -preset fast -crf 28 output.mp4
This would create a smaller file that is easier to stream without sacrificing much quality.
Conclusion
The ideal size for encoding X265 with FFmpeg is subjective and varies based on the video's purpose, target resolution, and quality requirements. By carefully selecting your CRF value and understanding the implications of resolution and bitrate, you can achieve a satisfactory balance between video quality and file size.
For further reading, consider checking out these resources:
By leveraging the powerful encoding capabilities of FFmpeg and the efficiency of the X265 codec, you can optimize your videos for a range of applications while maintaining excellent quality. Happy encoding!
