NVENC h265 has as lossless flag, a mode where no quantization happens, but search algorithms used to find exact matches for pixels continues to happen. So yes this is lossless compression.
My suggestion: Topaz gives us the possibility to output h265 losslessly by simply introducing a lossless checkbox that can be selected , this tells the encoder the following command:
preset=lossless
Yes it’s that easy. It seems to be NVENC 265 lossless encoding is a bit more efficient than FFV1 , file size is a least 10% smaller than FFV1
x265 codec has a lossless flag too, for example Handbrake. Simply write “lossless” into the Advanced Option field. When lossless flag is set, Quality settings have no effect.
Edit: Take care you have enough free storage space when doing lossless
It seems x264 has no lossless flag, but I’m not sure. For sure x265 has one. There are several forum threads around when you set x264 and CRF=0 Avisynth, Handbrake… the result is real lossless or not, for me it’s not clear, the thing is does quantization happen.
Back to NVENC, my 265 lossles encodes, gets up to 20% smaller than same files FFV1 encoded. NVENC-265 was much faster than FFV1, when you have an usable GPU.
If Topaz gives us a NVENC-265 lossless option for sure output files gets very large, for example when you do 4k upscale. But user is king, they could warn us, ideally by checking whether there is enough storage available on the selected target volume. A predicted file size pre-calc of lossless encodes is easy because they can use constant factor multiplied by resolution and fps
Definitely would be nice. I was using 120M CBR h264 for a while and that is pretty close, but definitely wastes disk space. Now I am just using high quality h265 for 4K and ProRes HQ for 1080p or less. I know ffmpeg does lossless h265 with lossless=1 and h264 with CRF=0 but I am not positive if it is compatible with the nvenc encoder.
I tried to add NVENC h.265 lossless compression to TVAI (not too complex to do) but found that it compresses worse than FFV1, even with the best preset (p7). Difference is like 10-15%. Key point here is NVENC, because with x265 situation changes to opposite, but it is not possible to add x265 as compressor to TVAI, at least not so easy. Maybe NVENC HEVC could give some small improvement in speed when the FFV-on-CPU is the limiting factor, but in my system there was no difference, because video processing is limiting speed, not video compressing.
