Quote:
Originally Posted by Marsu42
=> QUESTION: Is there a low source bitrate threshold like 3-5 MBps that could result in _worse_ transcoding quality AVC=>HEVC than AVC=>AVC? Or is HEVC encoding too similar to AVC so it doesn't make a difference?
I'm thinking of the different artifact types, which is why transcoding different image formats like dct-jpeg and wavelet-jpeg2000 isn't a good idea with low quality sources.
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I got what you mean, but most of the time it's not a matter of codecs, it's a matter of transform.
The reason you get way worse result if you encode an image in JPEG first and then JPEG2000 is that JPEG uses the Discrete Cosine Transform while JPEG2000 uses the Wavelet Transform, so you'll end up with the worse of them both. Anyway, in case of H.264 and HEVC, the Transforms are quite similar: DCT and Hadamard for H.264, DCT and DST for H.265 HEVC, so you won't notice an added detail loss caused by the math behind it if you use H.265 instead of H.264 or vice-versa but you will see the one introduced by the fact that you're making the lossy of the lossy, so quantization etc (i.e you're gonna lose something anyway no matter what). The thing is that linear algebra wise, though, you're fine; I hope that answers your question.