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Old 12th April 2018, 08:57   #1  |  Link
TEB
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HRD=1 fails

hi! Im trying to force x265 to enable HRD info in my encodes. My packager requires it.

Using this string:
"ffmpeg -i source.mp4 -pix_fmt yuv420p -codec:v libx265 -x265-params rc-lookahead=50:keyint=100:min-keyint=50:hrd=1 -preset slow -crf 20 -force_key_frames "expr:eq(mod(n,50),0)" -c:a copy -y test1.ts "

Packager complains about no HRD info
Mediainfo shows no_hrd

I get this warning from libx265: x265 [warning]: NAL HRD parameters require VBV parameters, ignored

How do i interpet this one ? Why do i need a vbv buffer defined when i only need the information so that the packager can understand the bitrate in the ES

/TE
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Old 13th April 2018, 01:51   #2  |  Link
foxyshadis
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Because HRD info's only use is to explicitly state the size of the buffer and tell the decoder how full it should be regularly. HRD exists so that tools can automatically verify that the stream you generated actually conforms to the memory restrictions you needed, beyond the simple level and profile limits, not to get the bitrate for the stream. And ultimately, that's so that you can verify that the viewer can actually watch the video without stuttering.

If you actually have no hardware limits and the verification is a formality, just set a gigantic vbv-bufsize and vbv-maxrate. 1000000 should work nicely, unless you think you'll ever actually hit 1gbps. If the packager kicks back an error about the size, then you can figure out what it wants.
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Old 13th April 2018, 12:27   #3  |  Link
TEB
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thx Foxy
It baffles my how crappy many of the commercial packagers are regards conformity of the pre-encoded streams.
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