I know this may sound like a weird statement coming from the author of FastFlix, but from the bottom of my heart, please stop the needless pixel loss! Every time you re-encode (aka transcode) a video it losses information, which lowers the quality and makes it a lot worse if you ever need to do it again. Re-encoding makes you a pixel killer!
Why am I saying re-encoding and not just “encoding” when you may have the original video? Sadly, to even fit onto your computer or device the video you are working with has already been encoded in a highly compressed manor. Even phones and professional cameras like the RED series use real-time compression. Raw video takes too much bandwidth for standard storage media. For example, imaging recording raw video using a video sensor at 16-bit 60FPS. A single minute of UHD footage would be near 60GB! That translates into a bitrate of over 7,500,000 kbps. Compare that to a re-encoded YouTube video of HDR 60FPS 4K footage is around 30,000 kbps, 250x times less quality!
Why does it matter?
Everyone has seen potato quality images and videos being re-shared again and again. The quality loss is due to needless re-encoding.
Websites generally always re-encode videos for a variety of reasons, such as adding watermarks or forcing certain bitrates. It may be required in some instances, but for most cases it’s overkill. If I had the power I would challenge websites to instead publish what encoding targets are required and allow for direct playback of the original file.
But while we don’t have control over that, that makes it even more important to not make it worse when you have control over it.
In the above example I took a short video and encoded it again and again and again using the same settings each time. The video still looks good while being watched, but if you zoom in you can see the entire thing has essentially become blurred. Don’t do this to your own videos, save the pixels!
There are some cases that it cannot be avoided that we will cover later, but even common operations like trimming videos and rotating them can be accomplished without re-encoding.
Trim and Rotate without re-encoding
Two very common reasons people want to re-encode videos is to shorten them to a particular section, or rotate it the proper direction. Thankfully you can do both of those without modifying the original video stream. I am using the command line tool
ffmpeg to accomplish this, which is available for free.
To rotate the video, you just have to add some metadata to the container the video is in. This is how phones set videos to portrait or landscape mode without having to change their encoder settings.
ffmpeg -i your_video.mp4 -metadata 0:s:v rotate=90 -map 0 -c copy rotated_video.mp4
In the above example, replace
your_video.mp4 with the video file you need rotated. It will be copied with the new metadata to
rotated_video.mp4 and now should be rotated properly.
To cut out a section of the video, you simply need to “copy” everything between the two desired points. For example if you want to cut out a 48 second section between
1:50 (one minute two seconds and one minute fifty seconds), use the following command.
ffmpeg --ss 1:02 -to 1:50 -i your_video.mp4 -map 0 -c copy rotated_video.mp4
Are there any exceptions?
There are a few cases where you simply cannot avoid re-encoding. If you need to add effects, crop, make any actual modifications to the video, you will need to re-encode.
However if you are keeping the video as is, there are only three instances you should consider re-encoding for:
- Limited bandwidth scenarios
- Device compatibility
- Cannot provide required storage space
Limited bandwidth scenario
ISPs still like to pretend upload speeds don’t matter. Even if an ISP provides 1Gbps down most still have less than 45Mbps upload peak. Things get even worse for mobile, where the average upload rate is around 10Mbps. Then on top of that, a general rule of thumb is your video bitrate should be around half or less of available bandwidth to ensure there isn’t stuttering.
That means if you’re planning to share videos in real time with the world, you simply have to re-encode (transcode) it.
There are some large companies that have terrible compatibility with commonly accepted formats to be anti-competition. That means if you or a loved one is enslaved to some large fruit company, you may need to tinker with your videos to please the orchard overlords.
“Storage is cheap” is a phrase I hear a little too much in the coding world. In the real world without a large quarterly tech budget, you have to count your pennies. If you can re-encode a video so that it’s near visually lossless while saving on storage space for your needs, go for it!