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Transcoding from 4:2:2 to 4:2:0 without any other loss of quality

Added by Petar Ivanov over 7 years ago

I want to transcode 4:2:2 to 4:2:0 channels without any other loss like resolution or bitrate ?
Anyone know how to make with TVH or with ffmpeg in TVh with pipe from HTTP to output same HTTP ?


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RE: Transcoding from 4:2:2 to 4:2:0 without any other loss of quality - Added by Stephen Neal over 7 years ago

It's not really possible to guarantee no loss of quality. Whatever you do you are decoding and recoding - and that will give you a quality hit.

Also given that 4:2:2 has twice the vertical chroma resolution as 4:2:0 - you are going to get a quality drop in vertical resolution terms IF you go from interlaced to interlaced. One way round this is to deinterlace to progressive - as although you are still running at 4:2:0, you are running so at a higher vertical resolution effectively

I've not done this in TV Headend - but I've taken 38Mbs H264 4:2:2 1080/50i stuff - which is 1920x540 Y and 960x540 Cr Cb detail for each 50Hz field, and de-interlaced this to 1080/50p 4:2:0 which is 1920x1080 Y and 960x540 Cr Cb detail for each 50Hz frame (retaining as much chroma resolution as possible). If you transcode to 4:2:0 1080/50i you end up with 1920x540 and 960x270 for each field.

I did this using a W3FDIF (Weeston 3 Field Deinterlace Filter) in ffmpeg, and went for an increased bitrate over the source. The resulting 4:2:0 1080/50p stuff played fine on a Raspberry Pi Zero - which would have had no chance of playing the 4:2:2 sources.

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