![]() It is a single file and will be treated as any other file – text, data, etc. Imagine downloading a video file from Dropbox, S3, or Google Drive. However, it would be very hard to do this if the entire file was being streamed in one go. What is MPEG-DASH (Dynamic Adaptive Streaming Over HTTP)?Īs we learned in the previous section, ABR or Adaptive Bitrate Streaming is used for dynamically varying the video bitrate and quality during streaming in response to the changes in bandwidth and buffer fullness at the player. Note: Take a look at our deep dive into ABR streaming for more details. With that introduction to ABR, let’s now see how MPEG-DASH facilitates ABR streaming. This is how the bitrate and quality are adaptively varied to adapt to the varying bandwidth conditions. This process continues throughout the video. It then receives and plays back the 4 mbps chunk. If the bandwidth suddenly drops to 5 mbps, then the player will probably request for the 4 mbps chunk from the server because it is risky to ask for the 5 mbps chunk. Then the player senses the bandwidth again and if it is still very high, it asks for the highest bandwidth again. So, the player safely downloads the highest bitrate, 5 mbps for the first segment/chunk (perhaps, 6 seconds long). This is much greater than the highest bitrate viz. When the player starts to playback the video, it senses the available bandwidth and let’s assume its 20 mbps. ![]() Let’s assume that the video has been encoded at the bitrate ladder shown above. A collection of renditions is a bitrate ladder. In ABR streaming, a video is transcoded into multiple resolutions and bitrate combinations and each is referred to as a “rendition”. It is the process by which the quality and bitrate of video delivery are adaptively varied to match the bandwidth conditions and ensure smooth delivery over the internet. No magic here □ĪBR stands for Adaptive Bit-Rate streaming. If you understand ABR streaming well, then MPEG-DASH simply describes the mechanics of ABR – that’s all. ![]()
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