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@@ -23,31 +23,31 @@ In order to prepare content for delivery by [adaptive bitrate streaming](https:/
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You should be aware of the content you are processing, and customize/tune the encoding ladder to the complexity of the individual video. At each resolution, there is a bitrate beyond which any increase in quality is not perceptive – the encoder operates at this optimal bitrate value. The next level of optimization is to select the resolutions based on the content – for example, a video of a PowerPoint presentation does not benefit from going below 720p. Going further, the encoder can be tasked to optimize the settings for each shot within the video.
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Microsoft's [Adaptive Streaming](autogen-bitrate-ladder.md) preset partially addresses the problem of the variability in the quality and resolution of the source videos. Our customers have a varying mix of content, some at 1080p, others at 720p, and a few at SD and lower resolutions. Furthermore, not all source content are highquality mezzanines from film or TV studios. The Adaptive Streaming preset addresses these problems by ensuring that the bitrate ladder never exceeds the resolution or the average bitrate of the input mezzanine. However, this preset does not examine source properties other than resolution and bitrate.
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Microsoft's [Adaptive Streaming](autogen-bitrate-ladder.md) preset partially addresses the problem of the variability in the quality and resolution of the source videos. Our customers have a varying mix of content, some at 1080p, others at 720p, and a few at SD and lower resolutions. Furthermore, not all source content is high-quality mezzanines from film or TV studios. The Adaptive Streaming preset addresses these problems by ensuring that the bitrate ladder never exceeds the resolution or the average bitrate of the input mezzanine. However, this preset does not examine source properties other than resolution and bitrate.
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## The content-aware encoding
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The content-aware encoding preset extends the "adaptive bitrate streaming" mechanism, by incorporating custom logic that lets the encoder seek the optimal bitrate value for a given resolution, but without requiring extensive computational analysis. This preset produces a set of GOP-aligned MP4s. Given any input content, the service performs an initial lightweight analysis of the input content, and uses the results to determine the optimal number of layers, appropriate bitrate and resolution settings for delivery by adaptive streaming. This preset is particularly effective for low and medium complexity videos, where the output files will be at lower bitrates than the Adaptive Streaming preset but at a quality that still delivers a good experience to viewers. The output will contain MP4 files with video and audio interleaved
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The following sample graphs show the comparison using quality metrics like [PSNR](https://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio) and [VMAF](https://en.wikipedia.org/wiki/Video_Multimethod_Assessment_Fusion). The source was created by concatenating short clips of high complexity shots from movies and TV shows, intended to stress the encoder. By definition, this preset produces results that vary from content to content – it also means that for some content, there may not be significant reduction in bitrate or improvement in quality.
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**Figure 1: Rate-distortion (RD) curve using PSNR metric for high complexity source**
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**Figure 2: Rate-distortion (RD) curve using VMAF metric for high complexity source**
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Below are the results for another category of source content, where the encoder was able to determine that the input was of poor quality (many compression artifacts because of the low bitrate). Note that with the content-aware preset, the encoder decided to produce just one output layer – at a low enough bitrate so that most clients would be able to play the stream without stalling.
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**Figure 3: RD curve using PSNR for lowquality input (at 1080p)**
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**Figure 3: RD curve using PSNR for low-quality input (at 1080p)**
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**Figure 4: RD curve using VMAF for lowquality input (at 1080p)**
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**Figure 4: RD curve using VMAF for low-quality input (at 1080p)**
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