Handbrake upsizing video bitrate

General questions or discussion about HandBrake, Video and/or audio transcoding, trends etc.
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mydarkpassenger
Posts: 2
Joined: Mon Sep 08, 2014 3:43 pm

Handbrake upsizing video bitrate

Post by mydarkpassenger »

I am trying to shrink the size of some rather large video files while retaining a video quality of no more than roughly 2000 bitrate at the most. I set the video quality of the profile to a constant quality of 23. The video file has a bitrate of 5000 or so and after I processed it the file jumps to a bitrate of over 7000. I can drop the quality but then if I run another file with a lower bitrate against it, the quality will get quite a bit worse. If I set an average bitrate for the conversion of 2000 then files with a lower quality will get bigger. I'm not even sure why Handbrake is increasing the bitrate since I doubt it's increasing the quality.

Is there a way to set a max bitrate on a conversion without dropping or raising the bitrate on files with a lower bitrate?
mduell
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Joined: Sat Apr 21, 2007 8:54 pm

Re: Handbrake upsizing video bitrate

Post by mduell »

You can abuse vbv to do this.

Bitrate isn't quality across different videos.
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JohnAStebbins
HandBrake Team
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Joined: Sat Feb 09, 2008 7:21 pm

Re: Handbrake upsizing video bitrate

Post by JohnAStebbins »

I'm not even sure why Handbrake is increasing the bitrate since I doubt it's increasing the quality
You assume correctly that HandBrake can't increase the quality. When a video is recompressed to a "higher quality" than the original, all you are doing is faithfully preserving all the compression artefacts that were in the original video.

When re-encoding video, the original video is decompressed frame-by-frame and then recompressed. The encoder doesn't know anything about the original bitrate or quality of the video. It only sees raw uncompressed frames.

If you have videos of varying low-ish quality and you don't want the transcode to have a higher bitrate than the original, all you can do is tweak the quality for each transcode get the bitrate you want. A good rule of thumb is that a 6 point change in RF will roughly halve/double bitrate and filesize.

Also, as mduell points out, if you are attempting to transcode to a lower bitrate than the original and you have a specific max bitrate you would like to enforce, VBV settings are the way to go. http://www.chaneru.com/Roku/HLS/X264_Se ... bv-maxrate

With VBV and quality based encoding (RF values), the enocder will use lower bitrates where it can (in less complex scenes), but where higher bitrates are needed it will cap bitrate at the VBV settings specified.
rollin_eng
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Posts: 4836
Joined: Wed May 04, 2011 11:06 pm

Re: Handbrake upsizing video bitrate

Post by rollin_eng »

Could you please post your HB logs, instructions can be found here:

https://handbrake.fr/docs/en/latest/hel ... y-log.html
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