It’s just a matter of English, really.
Every video is a message (or a signal, like we’ve seen in Signal, from Driving Miss Digital). When you shoot video, what you get in-camera or through SDI or HDMI, etc., can be said to be the original message.
This message has to be converted from photons of light to electrical pulses to a digital file format. Encoding is what happens from the second stage to the third stage.
Prefix ‘En’ – to put into or cause to be something. Examples – Enslave (make a slave), endear (make one dearer), envision (put into vision), and so on.
When you convert an original (I repeat: Original) message (signal, letters, music, whatever) to another form, you are said to be encoding. I use it with the condition that this is the first time the original message is being coded.
When your camera converts imagery into a file format, it is said to have encoded the video. First time.
So, H.264, AVCHD, XDCAM, Prores, etc. – they have already been encoded for your viewing pleasure.
Spanner in the works: What if you shift the ‘first’?
Some people might say the file written by the camera is the first message, and any further coding (conversion) that takes place can be called encoding. E.g., a DP might consider encoding to happen in camera, while the editor (who only receives the digital file) is correct to assume what he/she has in hand is the first message. A DCI post house might view the master as the original file, which needs to be encoded for digital cinema.
There’s no right or wrong here. I explicitly use the word encoding to signify the first conversion which happens in camera. When a camera does multiple conversions, each file is encoded separately. After all, they are two different files or videos anyway so there’s no need to be confused.
What if a camera encodes to one file format, and then uses this file for a second conversion, all in-camera? You get two file formats out of the camera, but you don’t know how each one was made. If the camera manufacturer explicitly declares what is happening inside, you will have your answer. Otherwise, assume both are being encoded.
Prefix ‘Trans’ – meaning across or beyond. Examples – Transform (from one form to another), transatlantic (across the Atlantic), transgender (between genders), and so on.
Every subsequent coding (conversion, transformation) of a file format to another is transcoding. This is the meaning with which I use the term.
It assumes that you have a file that can be directly converted to another. Key word being ‘directly’.
Spanner in the works: How direct is ‘direct’?
When you convert a file directly, one assumes no changes can be made to the message itself. If a spy encodes a message, the form of the message changes so that an outsider will not know how to decipher it. However, the original message is still within the cipher, and does not change. That’s the point.
But what happens when you transcode a 25p file to 24p? Has the original message changed, or not? What happens when you downsample from 1080p to 480p? Has the meaning changed, or not? Technically tough questions, for which there are no solid answers.
If the ‘intent’ of the filmmaker hasn’t changed, I assume a transcode is the right term to use. I don’t mean final intent, only original intent. We’re not talking about the final edited and finished piece, only the file or shot in question. It’s a bit fuzzy, but that’s all we have to go on.
If the intention is to preserve the original message, just in another form that’s all, it is transcoding.
Render – Give, Draw. Examples – Rendering a service, rendering a painting, and so on
When many files are chopped on the editing timeline, and it’s time to create a new file which incorporates all these changes, we are ready for rendering. If we only want to observe a small portion of the timeline (maybe we’ve added a tiny effect and want to see the results), we are still rendering.
Spanner in the works: Why not transcoding?
This is where ‘intent’ comes into play. I use the term rendering to signify any coding (conversion, transformation) that a happens to change the original message. Adding effects, filters, transitions, etc., all change the original shot into something new. The intention is not to preserve the original message but to make something new from it.
Making computer graphics (CGI), adding titles – any ‘drawing’ whatsoever – will all inevitably lead to rendering.
Interpolation, or upscaling (upsampling, whatever you want to call it) is not rendering, because you are trying to preserve the original message. Changing the frame rate is not rendering because you are not changing the intentions of the shot.
Rendering always means something new has been added. The message or video has changed.
Spanner in the works: Does the computer think I’m right?
No. Whenever any change has to be made, the computer must recalculate and redraw. To a computer, everything is rendering. If you are sitting within a group of visual effects artists, then the term might be more overreaching than what I use it for.
Hey, who said language is perfect? These are not terms etched in stone. Even dictionaries disagree sometimes as to meanings of terms. I’ve shown you how I use it, nothing more is implied.
Export – bringing or taking out from one place to another. Examples – exporting goods from one country to another.
An export can be an encode, transcode or render, depending on what you’re trying to do. However, it only applies to applications or programs, and not to the conversion itself.
Only an application can export something. E.g., if you have a locked edit sitting on a timeline, this is within the NLE. Exporting is the process of coding (converting, transforming), and many other things. The NLE ensures metadata is written, effects are rendered, and so on.
Spanner in the works: What about encoders? Aren’t they applications?
Of course they are. If you open an encoding application to transcode a video to another format, you could use the ‘Export’ command or function within the application.
So, if you’re having dinner with a bunch of programmers or encoders, the word ‘export’ might be better, since they know the application in question. Next day morning, if you’re having breakfast with filmmakers, they might not understand why you’re using the term ‘export’ when all you’re doing is transcoding!
Second Bonus: Decoding
So, what about decoding? Does it apply to video?
Unfortunately, due to the nature of the conversion, something is always lost:
- Light – Electricity (Energy is lost when converted from one form to another)
- Electricity to Signals (Sampling)
- Signals to Files (Sub-sampling, Compression, etc)
Once a file has been encoded, you can never get back the original. It is to preserve the original in memory that we record images and sound.
To recap, here’s a quick overview:
If love is the intent, it is converted into a message (understandable or useful form). This is encoding.
Encoding one message form to another is transcoding.
Changing the intent of the original message is rendering.