4 Digital Video

Video frames and settings

Digital video is a sequence of still images called frames. Displaying frames rapidly creates the impression of motion.

A video's main characteristics are independent settings:

• Frame size (resolution): The number of pixels in each frame, written as width by height. A frame size of $1920 \times 1080$ is commonly called 1080p; $3840 \times 2160$ is 4K UHD.

• Frame rate: The number of frames displayed per second, measured in fps. Common rates are $24$, $25$, $30$, and $60$ fps. Higher rates can make fast motion look smoother, and footage recorded at a higher rate can also be slowed down during editing.

• Aspect ratio: The frame's width compared with its height. A $16:9$ frame is widescreen, while $9:16$ is vertical. Choose a ratio suited to the intended screen and platform.

• Scan type: Progressive video displays complete frames in sequence; interlaced video divides each frame into alternating fields. Progressive video is the usual choice for contemporary web delivery.

Plan these settings around the final destination, and keep project settings consistent with the footage when possible. Changing frame rate during editing can require frames to be repeated, blended, or removed.

Recording usable footage

Before recording, decide where the video will be viewed and choose a suitable orientation, frame size, and frame rate. Record a short test and check that both picture and sound are clear.

During a take, keep the camera steady, using a tripod or stable support when practical. Check focus and exposure, and look for distracting backgrounds or harsh lighting. Leave a little extra footage before and after the action so clips are easier to trim.

Record clear sound: move the microphone closer to the speaker when possible, and listen for noise or distortion. Organize the clips and make a backup of the original files before editing.

If clips have different frame rates or dimensions, check that they display and play as intended in the editing project. A sequence is the timeline where video, audio, titles, and effects are assembled.

Editing and arranging video

A typical editing workflow moves from organizing the material to reviewing the finished sequence:

1. Import and organize recorded clips, audio, graphics, and other assets.

2. Create a sequence with the intended frame size, frame rate, and aspect ratio.

3. Select and arrange shots on the timeline in a clear order that tells the story.

4. Trim the beginnings and endings of clips, remove unwanted sections, and refine cuts between shots.

5. Improve the presentation by adjusting sound levels, correcting color or exposure, and adding titles or transitions where they help the viewer.

6. Review the full sequence for mistakes, abrupt cuts, missing media, and sound that is too quiet or too loud.

A direct cut joins one shot to the next. A transition, such as a dissolve, changes gradually between shots; use transitions purposefully because too many effects can distract from the content. Most editors arrange clips across multiple video and audio tracks, allowing titles, music, narration, and images to be layered.

Containers, codecs, and compression

A container packages a video stream, audio, and related information into a file. MP4 and MOV are common containers. A codec, or coder-decoder, compresses and decompresses media; H.264 and HEVC/H.265 are common video codecs. The container and codec are different choices: an MP4 file can contain video and audio encoded using particular codecs.

Compression reduces the data needed to store or transmit video. Lower data rates generally produce smaller files, but excessive compression can make details look blocky or blurry. Bitrate is the amount of data used per second of video: a higher bitrate can preserve more detail but also creates a larger file. Variable-bitrate encoding can allocate more data to complex scenes and less to simple ones, balancing quality and file size.

Exporting and checking the finished video

Choose export settings for the intended use:

• Format and codec: H.264 in an MP4 container is a widely supported choice for online video.

• Frame size and frame rate: Match the project and delivery requirements; avoid changing them without a reason.

• Aspect ratio and orientation: Preserve the intended shape, and do not stretch the picture to fit.

• Bitrate or quality preset: Use enough data to retain acceptable detail while meeting file-size or upload limits.

• Audio: Select a compatible audio codec and confirm that the sound is present and correctly mixed.

For example, a web video edited at $1920 \times 1080$ and $30$ fps could be exported as progressive H.264 in an MP4 file, with a bitrate suitable for its destination. YouTube recommends uploading video at the same frame rate at which it was recorded and provides separate bitrate guidance by resolution and frame rate; actual platform requirements can differ.

Check the delivery platform's current specifications, then watch the exported file to verify that it plays correctly. Reviewing the finished file, rather than only the editing timeline, can reveal playback, picture, or sound problems.