Why Compression Matters (MMM#47)
Greetings everyone,
Madeline here, back with the 47th entry in The Movie Minute. For this entry’s topic, we’ll be touching on something more technical but important- media compression!
You’ve probably encountered a message about a file being too large to upload- and even if you don’t encounter that message, whenever you upload a video or a photo to social media, it likely compresses the file before posting. That’s because for efficient delivery and streaming across the web, media has to be made smaller while still maintaining the same apparent quality. But not all compression is the same- that’s why we’re here to discuss the different ways media is compressed.
There are two main types of compression: lossless and lossy. Lossless compression attempts to shrink the file size while retaining an exact copy of all the original data. Lossy compression, on the other hand, results in a file that contains only an approximation of the original data, but results in far smaller file sizes. Think of a raw or losslessly-compressed file as an original painting, or a lossy-compressed file as a photocopy of a painting.
For video, raw footage size can vary depending on the camera and chosen format. For example, the Panasonic GH5 has lower file sizes due to having a more efficient bitrate made possible by its Micro Four Thirds sensor, while footage from the Sony FS7, which uses a Super 35 sensor, has larger file sizes and bitrates, especially when shooting in LOG. As editors, it’s important to have all the raw video and audio that way we have as much control and material as we can to produce a full video, with compression being a concern when the time comes to export for delivery. The most common format for online video delivery is H.264, which is used by major streaming services and social media sites, as well as Blu-ray. Other common formats are H.265, which is used in more premium streaming services as well as 4K Blu-rays, and AV1, a newer format that is open-source and claims better efficiency compared to H.264. In fact, when we upload full-res media that is usually exported in a match source-high bitrate set, the website (i.e. Vimeo) transcodes the video into several versions at varying resolutions to make online streaming of the video more efficient. While compression done right can result in no problems at all when playing the content, compressing too much or using an inefficient codec can produce unwanted visual artifacts such as banding, blocking, etc., like making a photocopy of a photocopy.
Audio compression is an important thing to note, too. WAV is definitely the most important format we want to start with, as it is usually the complete, original audio with all the data. RODE mic footage is recorded in this format, and any stock music we use is usually in WAV as well. While Artlist also offers music tracks in MP3, using lossy compressed audio can bear the risk of audio distortion and anomalies, which is why we wait until export time to worry about compression (the preset we use typically uses AAC format, which is more advanced than MP3) Many streaming services also use lossy audio formats such as AAC, or Dolby Digital (constant bitrate). On the other hand, lossless audio formats such as FLAC are often used for many music streaming apps as well as for home video through DTS HD-Master Audio or Dolby TrueHD (variable bitrate).
Photo compression is important as well. We typically take our photos and load them as raw image files, which are larger in size but contain all the information and metadata we need to transform them into amazing images. The specific raw image formats vary by camera, but the most common we work with are ARW from the A7IV and CR3 from the Canon EOS R. Loading these files into a program such as Adobe Lightroom Classic allows us to control and adjust the color and tone of each image before we export them for delivery. The two most common image export formats are PNG, which is lossless, and JPEG, which is lossy, with both having their own purposes. PNG is best for when file quality matters more than size, as it is less likely to contain visual artifacts, while JPG is great for when interacting with a platform where there is a limit to how big files can be (i.e. social media).
Overall, compression is an important part of how people share media, both casually and professionally. And as filmmakers and editors, it’s crucial that we understand and harness the right formats to effectively and efficiently deliver our stories to platforms where they can make an impact.
And that concludes this entry in The Movie Minute. Wishing you all the best, and see y’all in 2! -Madeline
We at Poor Bear Stories are passionate about your story. Creating media that makes a difference is our craft and life’s work. With over 35 years of industry experience, we bring a host of solutions to your brand and media endeavors.
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