I don't think they'll do so today, especially since most replay is today done with HW-support for decoding, anyway.īut the ffmpeg executable on its own (and also ffplay) will not use "pp" by default. In the past, especially when MPEG-4 ASP and xvid were popular, some software (like mplayer and VLC) chose to insert the "pp" filter to the processing chain by default when they played back files using the ffmpeg library.
If you refer to the video filter named "pp" - that filter is not a default part of the processing chain when invoking the stock ffmpeg executable. The one that is an integral part of the h.264 standard decoder is, of course, being used, as without it the decoding would just fail. In practice, this would look nearly indistinguishable from full 10-bit 4:4:4 What deblocking filter are you refering to?
While the luma blocks would contain genuine 10-bit data, the chroma blocks would contain the original 8-bit values. To make use of this technique, you'd need a custom decoder that works directly in YUV color space with the original 8-bit 4:2:0 H.264 video to produce the equivalent of a decoded 10-bit 4:4:4 H.264 video. Rather than averaging in artifacts from adjacent macroblock edges, it's better to combine 2x2 arrays of luma values within each macroblock. The reason you'd want to use direct 2x2 summing rather than bilinear or biqubic interpolation is because of the geometric macroblock tiling of the H.264 frame. The major advantage is that the original precision of the data samples is preserved without averaging - the only thing that is downscaled is the spatial resolution of the image. Each 2x2 block of 8-bit luma pixels would then be summed to produce a single 10-bit subsampled luma pixel. The luma macroblocks would be decoded into 8-bit monochromatic pixels. Since the UV chroma data is already subsampled at half the horizontal and vertical resolution as the Y luma data, the chroma data could be used directly as 8-bit 1080p 4:4:4 UV data without resampling it. Downscaling an H.264 video frame by precisely 50% from UHD->1080p presents the option of working directly with the 4:2:0 YUV data decoded from the H.264 file.
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