Exercises: Image, audio and video editing

State what type of content each of these files holds and give a typical example of use for each: "photo.jpg", "song.mp3", "video.mp4", "logo.png", "notes.odt", and "trip_photos.zip".

A photo of $12\ \text{MB}$ cannot be attached to a form that only accepts files up to $2\ \text{MB}$. Explain two different ways to reduce the file size and what is lost in each case.

These basic steps in video editing are in the wrong order: (a) export the result, (b) cut unwanted parts, (c) import the recorded clips, (d) add titles and music, (e) arrange the clips on the timeline. Put them in the correct order and explain in one sentence what is done in each step.

A photo has a resolution of $1920 \times 1080$ pixels. Explain what these two numbers mean and reason what will happen to the quality if we enlarge a small photo of $320 \times 240$ pixels significantly to use it as a cover.

To show the teacher an error message on your computer, you can take a photo of the screen with your phone or take a screenshot. Explain what a screenshot is, how to take one on a computer, and why it is usually a better option than a photo.

Explain the difference between cropping an image and resizing it, and decide what you would do in each case: (a) you want to remove a person standing in the background of a group photo, and (b) you want the photo to take up less file space while keeping everything that appears in it.

A classmate sends you a video and it "will not open" on your computer, even though it works fine on theirs. Explain how formats and codecs relate to this problem and give two possible solutions.

When recording audio with the input volume set too high, the voice sounds distorted even if you turn down the speaker volume afterwards. Explain what clipping/distortion is during recording, why it cannot be fixed later, and how you would prevent it when preparing the recording.

The figure shows the timeline of an end-of-year video edit, which must last $90\ \text{s}$ in total, but one clip is missing.

Calculate how many seconds the missing clip must last for the complete edit to last exactly $90\ \text{s}$, and explain where you would place the end credits on the timeline and why.

You recorded an interview on your phone for an assignment and there is a lot of street noise in the audio. Describe what basic audio editing adjustments you would try to improve it, in what order you would apply them, and what precaution you would take to avoid distorting the voice.

Explain the difference between lossy and lossless compression formats using these pairs: .jpg vs .png and .mp3 vs .wav. Then choose the most suitable format for each case and justify it: a logo with a transparent background, a photo for a website, a song to keep on your phone, and a recording that will undergo further editing.

A three-minute video edit uses twenty different transitions: wipes, spins, star wipes, and fades between all the clips. Analyse the effect this overuse has on the viewer and propose a transition rule for your class video, indicating which ones you would use and where.

More and more videos include subtitles. Explain two reasons why it is advisable to subtitle your class project video (think about accessibility and how videos are viewed on cell phones) and describe the two ways to generate them: automatic and manual, including their advantages and risks.

You have recorded a $5\ \text{min}$ video that takes up $300\ \text{MB}$ and you want to send it by email, but the attachment limit is $25\ \text{MB}$. Calculate how many times it exceeds the limit and explain two ways to get it to its destination without losing it, stating what is lost (if anything) in each case.

Two photos from the same school tournament turned out badly: one with the players looking very small and centred with a lot of empty floor, and another blurry and dark because it was taken in the late afternoon. Explain what basic framing and lighting advice you would apply to retake each one and improve them.

Your class wants to record a monthly ten-minute podcast. Design its structure (intro, two or three segments, outro), choose the audio format for publishing it, and describe the minimal editing you would do before uploading it.

You are going to produce a 2-minute video to present the secondary school to families. You have a technical limitation: if you record with mobile phones at maximum quality (4K at 60 fps), each minute takes up around 400 MB, but the school's communication platform only accepts files up to a maximum of 25 MB.

1. a) Predict what will happen if you try to upload the uncompressed video and calculate how many times you must reduce the original size to meet the platform's limit.
2. b) Design the technical production plan to solve this problem: specify what resolution (4K, 1080p, or 720p) and frame rate (fps) you will configure when recording or exporting, what container format and compression you will use to ensure compatibility with any mobile phone or PC, and what three editing decisions you will make so that the video is dynamic without shooting up the final file size.

A three-minute song takes up $30\ \text{MB}$ in .wav format and only $3\ \text{MB}$ in .mp3 format. Calculate how many songs of each type fit into the $1.5\ \text{GB}$ of free space on a cell phone, and explain what causes the huge difference in file size between the two formats.

Your group needs an attractive cover for a school video that will be published on YouTube and on the school's website. A team member suggests downloading a striking photograph found on Google Images taken by a professional photographer.

1. a) Explain what technical and legal consequences using that image would have if the author has all rights reserved (copyright), detailing how online platforms detect protected content.
2. b) Analyse two legal alternatives: explain how you would search for an equivalent image with a suitable Creative Commons licence (indicating what minimum conditions said licence must meet for this public school use) and describe how you could create your own cover combining graphic elements without infringing copyright.

To shoot a 30-second advert encouraging people to use the library, a team recorded directly without planning. The result is chaotic: shaky shots, unintelligible sound because the music drowns out the voice, and scenes that drag on for too long.

1. a) Justify why the prior design of a technical script or storyboard would have avoided these production errors.
2. b) Design the corrected technical storyboard of the advert by dividing it into exactly 5 or 6 scenes (adding up to 30 s in total). For each scene, you must detail: audiovisual shot type (wide shot, medium shot, or close-up), camera movement or position, visual description of the action, sound track (voice, effects, or music), and exact duration in seconds.

In the school's digital magazine, you have received a photograph in .jpg format that has passed through several mobile phones via WhatsApp before reaching the layout computer. When enlarging it to print the cover, it looks blurry and with artifacts or pixel blocks around the edges of the figures.

1. a) Technically explain what lossy compression is in the JPEG format and why the process of repeatedly forwarding, editing, and saving (generation loss) degrades the image.
2. b) If you had to send the original file from the camera so that it does not suffer any alteration, describe two different technical transfer methods (indicating save formats or sending methods) that guarantee that the copy received is an exact clone of the original.

Your class is going to publish its technology projects both on YouTube (computer screens and TV, horizontal 16:9 format) and on Instagram Reels and TikTok (mobile phones, vertical 9:16 format).

1. a) If you record all the footage horizontally at 1080p (1920×1080 pixels), predict what will happen when trying to publish it in vertical format if you simply "stretch" it to fill the screen or if you do a "center crop", explaining what loss of information or visual distortion occurs in each case.
2. b) Design a technical production guide for the recording crew: what precautions must you take with framing during filming so that the same shot works for both formats, and what export parameters (pixel resolution and aspect ratio) will you configure in the editor for each platform.

Your group must choose the tool to edit a 5-minute educational Technology video that will be screened to the entire school community. You are considering two options:

• Option A: A free mobile app, very fast and intuitive, but which adds a visible watermark in the bottom corner and only allows exporting up to a maximum of 720p with 2 audio tracks.

• Option B: A free and open-source program for PC (such as OpenShot or Shotcut), without watermarks, with unlimited tracks and 1080p export at 60 fps, but which requires learning to use a complex timeline, and the classroom computers take quite a long time to render.

Critically evaluate which of the two options is more suitable for this project based on the visual impact, the required technical quality, and the available time, justifying your choice and explaining how you would mitigate the main drawback of the chosen option.

A student takes a photo in class of a distracted classmate, adds mocking elements using digital editing, and shares it on a public messaging channel. When confronted, they defend themselves by saying: "I took the photo with my phone, so the rights are mine, just as if I had taken a photo of a landscape."

1. a) Refute the student's argument technically and on a legal basis: distinguish between the intellectual property rights of the person taking a photograph and the right to one's own image and personal data protection of the person appearing in it.
2. b) Predict what ethical and disciplinary consequences the non-consensual dissemination of manipulated images can entail in the school environment, and draft a clear protocol of three rules for the correct use of cameras and photo editing at the school.