How do I convert 1080p 10bit mkv's to 720p 10bit?

[fighuass]

I also have audio and soft subs, the audio can stay the same and I want to keep the subs.
I don't have any example files right now, but I'll make good use of this information soon.

[_Al_]

You can use anything that loads that mkv and encodes at least video to 10bit as well , perhaps anything, megui, staxrip, ripbot,

Then you load result into mkvmerge, where you check video stream only, then you load that original mkv video and you uncheck that original video stream, keeping the rest.

[hello_hello]

Because Avisynth is 8 bit, I assume most Avisynth based GUI's will only output 8 bit video, even if they'll use the 10 bit x264 encoder. And even if the indexer/decoder (ffmsindex or L-Smash etc) can decode 10 bit video, they'd probably only output 8 bit for Avisynth. How much that matters, I don't know, as the 10 bit encoder should have advantages over 8 bit even when re-encoding 8 bit video, but I guess ideally you'd want to decode, process and re-encode while keeping it 10 bit all the way. I know there's a modified version of ffmsindex that'll output 10 bit (I'm not sure about L-Smash), but then you've stepped into the world of the 16 bit "hack" for Avisynth, which requires compatible plugins etc (can Avisynth itself even resize a 10 bit or 16 bit video correctly?)

I use MeGUI myself so I'm not very familiar with changes being made to other encoder GUIs, so I've no idea if any are capable of processing 10 bit video, or whether they all decode to 8 bit and then maybe have the ability to re-encode using the 10 bit encoder. MeGUI would decode to 8 bit and then re-encode as 10 bit.

[LigH.de]

No panic, hello_hello. You are confusing 8 bit resolution of uncompressed YUV video with 8 or 10 bit resolution of internal parameters of the encoded video stream after the sample-to-frequency-domain transformation. To gain precision, 10-bit encoded AVC does not even need more than 8-bit depth input. And who could originally provide high bitdepth material of a usual movie's playtime, anyway?

[hello_hello]

I'm mostly confused most of the time, but to clarify..... are you saying if I encode an 8 bit video with the 10 bit x264 encoder, and then later decode it to 8 bit, that'd produce exactly the same result as decoding it to 10 bit?

The OP wants to resize the video, if nothing else, but is there no advantage to decoding to 10 bit (or for Avisynth would it have to be 16 bit?) resizing, then encoding with the 10 bit encoder, or will decoding to 8 bit and resizing still produce the same result?

I've no idea if the OP's source is high bitdepth as such, only that it's 10 bit. If it's truly high bitdepth, I assume at least then 10 or 16 bit processing would be better?

[LigH.de]

Of course you may try to decode to high bitdepth, resize in high bitdepth, and encode again feeding high bitdepth into the 10 bit encoder. If you manage to do that correctly, which is very complicated IMHO, because AviSynth only supports 8 bits per component in uncompressed video. First you need a decoder which is able to produce a video output which can be handled as high bitdepth (I don't even know if either interlaced or stacked is preferred), then use filters which work in high bitdepth mode, and finally call the encoder so that it will interpret the AviSynth output as high bitdepth. That will be the most efforts for the littlest difference.

Yes, the results will differ. But I doubt you'll notice it as much as you may curse the additional efforts to make it work correctly.

I believe you misinterpreted "having a 10 bit encode" as "having an encode of high bitdepth material", which is probably not true. The original material was probably pretty usual, maybe a Blu-ray, just encoded with 10 bit internal resolution (AVC Main10 Level). I doubt it will make much sense to restore a raw YUV bitdepth which never existed before.

I believe the OP wants to convert AVC with Main10 Level in 1080 resolution to AVC with Main10 Level in 720 resolution; and I am quite certain that 8 bit resolution for the intermediate raw YUV video will be sufficient, because Main10 Level relates not to the bitdepth of the raw video, but to the frequency parameters after the transformation inside the AVC encoder, before quantization. Read again what the Fourier transform does, this is the best documented transformation from sample to frequency domain; AVC may use slightly different functions, but they are still very similar. The 10 bit are the resolution of the frequency parameters, not of the video components.

Don't shoot sparrows with cannons.

[hello_hello]

I believe you misinterpreted "having a 10 bit encode" as "having an encode of high bitdepth material", which is probably not true.

I probably assumed more than misinterpreted, not knowing anything other than the source being 10 bit.

I tried it once myself.... decoding, processing and re-encoding in high bitdepth, and while I was successful it involved a bit of "messing around" at the time, and there was an obstacle when it came to encoding the script via a GUI. From memory (it was a while ago) in the case of MeGUI it was not being able to change the command line in order to tell the encoder (or avs4x264mod) the output was 16 bit, or 10 bit, or something like that..... but at the time that was the obstacle. MeGUI can of course be used to encode with the 10bit encoder. I don't want to give the wrong impression there.