CS6250 Lesson 11: Applications: Video Test Guide 2026, Exams of Computer Networks

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CS6250 Lesson 11: Applications: Video Test Guide 2026

“1 I I I I I I I I I I I I I I I I I I I I I I I I al CS6250 Lesson 11: Applications: Video Test Guide 2026 Compare the bit rate for video, photos, and audio, - GORRECTANSWER Video - 2 Mbps Facebook photo gallery browsing (1 photo/s) - 320 kbps Music - 128 kbps What are the characteristics of streaming stored video? - CORRECT ANSWER -- Streamed - video starts playing within a few seconds of receiving data, instead of waiting for the whole file - Interactive - user can pause, fast forward, skip ahead, move back - Continuous playout - should play out the same way it was recorded What are the characteristics of streaming live audio and video? - GORREGHENSWERI- Many simultaneous users ~ Delay sensitive What are the characteristics of conversational voice and video over IP? - GORRECIANSWERI- Delay sensitive - Loss tolerant - the occasional glitch is okay How does the encoding of analog, audio work (in simple cerms)? - (SGRREGINANSWERE-Generally speaking, audio is encoded by taking many (as in, thousands) of samples per second, and then rounding each sample's value to a discrete number within a particular range. (This "rounding" to a discrete number is called quantization.) What are the three major categories of VoIP encoding schemes? - CORRECT ANSWER-1. Narrowband r I I I I I I I I I I I I I I I I I I I I I I I I L “1 I I I I I I I I I I I I I I I I I I I I I I I I al 2. Broadband 3. Multimode GORRESTANSWER! |. User location What are the functions that signaling protocols are responsible for? - the caller locating where the callee is. 2, Session establishment - handling the callee accepting, rejecting, or redirecting a call. 3. Session negotiation - the endpoints synchronizing with each other on a set of properties for the session. 4, Call participation management - handling endpoints joining or leaving an existing session. What are three QoS VoIP metrics? end-to-end delay - jitter - packet loss (CORREIA the cme eke What kind of delays are included in "end-to-end delay"? encode the audio - the time it takes to put it in packets, ~ all the normal sources of network delay that network traffic encounters such as queueing delays ~ "playback delay,” which comes from the receiver's playback buffer (which is a mitigation technique for delay jitter) - decoding delay, which is the time it takes to reconstruct the signal How does “delay jitter" occur? - GORRECTANSWER Between all the different buffer sizes and queueing delays and network congestion levels that a packet might experience, different voice packets can end up with different amounts of delay. One voice packet may be delayed by 100 ms, and another by 300 ms. We call this phenomenon "jitter," "packet jitter,” or "delay jitter.” r I I I I I I I I I I I I I I I I I I I I I I I I L a | How does the error concealment technique deal with packet loss in VoIP: CORRECT ANSWER - "Guessing" what the lost audio packet might be. This is possible because generally, with really small audio snippets (like between 4 ms and 40 ms), there's some similarity between one audio snippet and the next audio snippet. Could be repeating the previous packet or interpolating using the previous and next packets. What developments lead to the popularity of consuming media content over the Internet? CORRECT ANSWER 1. The bandwidth for both the core network and last-mile access links have increased tremendously over the years. 2. Video compression technologies have become more efficient. This enables streaming high-quality video without using a lot of bandwidth, 3. The development of Digital Rights Management culture has encterm-1Gouraged content providers to put their content on the Internet. Provide a high-level overview of adaptive video screaming, - GORREGMANSWERI-The video content is first created -- say in a professional studio like this lesson or using a smartphone by a user, The raw recorded content is typically at a high quality. It is then compressed using an encoding algorithm. This encoded content is then secured using DRM and hosted over a server. Typically content providers have their own data centers such as Google or use third-party Content delivery networks to replicate the content over multiple geographically distributed servers. This makes sure that the content can be delivered in a scalable manner, The end-users download the video content over the Internet. The downloaded video is decoded and rendered on the user's screen. Which protocol is preferred for video content delivery - UDP or TCP? Why? - GORREGHANSWER!-TCP, as data loss would make it difficult to reliably decode video data, TCP also provides congestion control, which is required for effective bandwidth sharing. What was the original vision of the application-level protocol for video content delivery, and why was HTTP GORREGIANSWERE The original vision was to have specialized video servers that remembered the state of the clients. These servers would control the sending rate to the client. In the event chosen eventually? chat the client paused the video, it would send a signal to the server and the server would stop sending video. Thus, all the intelligence would be stored at a centralized point and the clients, which can be quite diverse, would have to do a minimal amount of work. bua ee ee ee ee eee ee ee ee ee eee eee eee Ms ce eee ee a | However, all this required content providers co buy specialized hardware. Another option was to use the already existing HTTP protocol. In this case, the server is essentially stateless and the intelligence to download the video will be stored at the client. A major advantage of this is that content providers could use the already existing CDN infrastructure. Moreover, it also made bypassing middleboxes and firewalls easier as they already understood HTTP. Summatize how progressive download works. - SORREGISAINSWERE-The client sends byte-range requests for part of the video instead of requesting the entire video. Once the video content has been watched, the client sends a request for more content. Ideally, this should be enough for streaming without stalls. Toa buffer. ount for throughput variations, the client pre-fetches some video ahead and stores it in a playout GORRECTANSWER Content providers encode their video at multiple bitrates chosen from a set of pre-defined bitrates, Specifically, the video is chunked into How to handle network and user device diversity? segments which are usually of equal duration. Each of these segments is then encoded at multiple bitrates and stored at the server. The client request while requesting for a segment also specifies its quality. How does the bitrate adaptation work in DASH? - GORRECHANSWERA video in DASH is divided into chunks and each chunk is encoded into multiple bitrates. Each time the video player needs to download a video chunk, it calls the bitrate adaptation function, say f The function f that takes in some input and outputs the bitrate of the chunk to be downloaded. ‘What are the goals of bitrate adaptation? - SORRDCIANSWER!-1 Low or zero re-buffering: users typically tend to close the video session if the video stalls a lot 2. High video quality: the better the video quality, better the user QoE. A higher video quality is usually characterized by a high bitrate video chunk. 3, Low video quality variations: a lot of video quality variations are also known to reduce the user QoE. 4. Low startup latency: startup latency is the time it takes to start playing the video since the user first requested to play the video. bua ee ee ee ee eee ee ee ee ee eee eee eee Ds ce eee ee ee es