What is the most efficient multi-pass video encoding technique?

2 How does multi-pass encoding work?

Multi-pass encoding works by dividing the encoding process into two or more passes. Each pass has a different purpose and function. The first pass is usually the analysis pass, where the encoder scans the video and collects information about its features and statistics. The encoder does not produce any output in this pass, but instead creates a log file that stores the data for the next pass. The second pass is the encoding pass, where the encoder uses the log file to determine the optimal bitrate for each frame and segment of the video. The encoder then compresses the video and outputs the final file. Depending on the encoder and the settings, there may be more than two passes, such as a third pass for fine-tuning or a fourth pass for adding subtitles or metadata.

3 What are the benefits of multi-pass encoding?

Multi-pass encoding offers several advantages over single-pass encoding, which is the technique of encoding the video only once with a fixed or variable bitrate. Generally speaking, multi-pass encoding can achieve higher quality at lower bitrates, or lower file sizes at the same quality. Additionally, it allows you to have more control over the encoding parameters and options, such as target bitrate, quality factor, frame rate, resolution, aspect ratio, and audio settings. Furthermore, multi-pass encoding gives you more flexibility when it comes to encoding the video for different platforms and devices. You can encode the video with different formats, codecs, and profiles and adapt the output to the specifications and requirements of each platform and device.

5 How to use multi-pass encoding?

Multi-pass encoding is a technique that can be performed with various software and tools, such as ffmpeg, HandBrake, Adobe Media Encoder, or VLC. The exact commands may differ depending on the tool and codec, but the general procedure is similar. For example, when using ffmpeg and x264 codec for a two-pass encoding, you must first specify the input video file, the output format, the codec, and the target bitrate. You also need to add flags -pass 1 and -an to indicate that this is the first pass and that there is no audio output. For the second pass, you should change the flags to -pass 2 and -acodec copy to indicate that this is the second pass and that the audio is copied from the input. Additionally, you need to specify an output file name. Afterward, you must delete the log file and intermediate file created by the first pass. Lastly, you can check the output file and compare it with the input file. You should notice a noticeable improvement in quality and size.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?