October 24, 2020, 03:39:14 am

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Manual / Help to use Avidemux as beginner (Windows 10)

Started by conhelio, October 03, 2020, 08:50:05 am

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conhelio

Thank you! Honestly I have no idea why this video is in 4k resolution, while others (all produced from zoom recordings of conference sessions in the same way) are in 1920x1080. Having said that, I think reducing resolution would be the first step, can I do this with avidemux?

eumagga0x2a

Quote from: conhelio on October 16, 2020, 10:15:56 pmI think reducing resolution would be the first step, can I do this with avidemux?

Sure, please have a look at the "swsResize" video filter (you need to choose a video codec first, filters are not available in copy mode).

conhelio

Thanks, I tried with a short HD-testvideo. I don´t find swsResize Filter, but swScale (maybe because my language version of avidemux is German?). It allows to reduce resolution, but suprisingly a resolution to 45% (846x480 pxl) increases the filesize from about 35 MB to 43 MB. Apart from that, it works.

eumagga0x2a

Yes, the original English name is "swsResize", the German translation is "Bildgröße ändern (swScale)". libswscale (short: sws) is the library which does the job.

Quote from: conhelio on October 18, 2020, 09:50:29 pmsuprisingly a resolution to 45% (846x480 pxl) increases the filesize from about 35 MB to 43 MB.

Compressing with which encoder with which codec? If x264 --> H.264, then it is not surprising at all as I already mentioned how strongly compressed the source was. By all means, you need to do 2-pass encoding with given output size. I don't know whether this helps with that particular video, but you could additionally try to increase the number of reference frames to 5 as used by the source video.

Using HEVC would allow for a significantly better compression and quality, but HEVC is not universally supported by hardware decoders and very computationally expensive when decoded in software.

VP9 allows excellent quality, but the rate control seems to be very broken, the encoder is unbelievably slow in modes providing high quality while support by hardware decoders is even worse than for HEVC.