Finally, we produce the pairings by drawing the RQ curve for each resolution and extracting the convex hull.
Ffmpeg scale 720p 720p#
To recap, we use FFMPEG instructions to downscale the original file into the desired resolutions, encode each file with a range of QPs, and then upscale all the encoded versions to the native resolution to compute the PSNR with the source file (known as the reference). For example, set CRF in FFmpeg to reduce video file size (ffmpeg -i input.mp4 -vcodec libx264 -crf 24 output.mp4), resize 4K/1080p to 720p for smaller file size.
Ffmpeg scale 720p how to#
We showed how to display the best version of the requested source file on the client screen by picking the appropriate pair that suits the client’s limits in this short lecture. So, in order to request the proper version, the client selects the pair that best utilizes its bandwidth while maintaining the highest possible quality. This table is crucial to solving the problem of the two limitations mentioned before. We can build the table above using the convex hull, which associates each rate value with the relevant resolution. To calculate the PSNR, we introduce the following command: ffmpeg -y -i “VideoSource540p50_40_to_1080p.yuv” -i “VideoSource1080p50.yuv” -lavfi psnr=”stats_file=PSNR_File” -f null - Convex hull To downscale the sequence, use the FFMPEG command below: ff = FFmpeg(inputs=) ff.run() To make alternative versions, we need to change various settings, such as downscaling the sequence from 1080p to 720p or 540p, and encoding using QPs in the range of (to simplify).įollowing that, I’ll utilize FFMPEG (an open-source framework) python commands to demonstrate the various parts of the transcoding process. Consider a single scene in an FHD video source at 50 frames per second (i.e. The purpose is to create a database of bitrate/resolution pairs that the client may utilize to stay within its limits. Let’s take a closer look at the point where we encode our source with various parameters. Adaptive Bitrate streaming system Transcoding part
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