Opened 12 years ago

Closed 12 years ago

#3934 closed defect (fixed)

rc_max_rate parameter for h264 codec used in nuvexport's MP4.pm ffmpeg export module is out of date

Reported by: Thomas <tlunde@…> Owned by: xris
Priority: major Milestone: unknown
Component: perl / nuvexport Version: head
Severity: medium Keywords:
Cc: Ticket locked: no

Description

Line 226 of MP4.pm reads:

.$self->param('rc_max_rate', 768)

This line comes into play when the h264 codec is chosen in invocations of the iPod or MP4 presets built into nuvexport. It does not matter whether VBR or CBR is chosen. It does not matter whether "iPod compatibility ?" is chosen or not. This is wrong.

If CBR is chosen, this parameter should either be left out or set equal to the value given.

If VBR is chosen and iPod compatibility is not, this parameter should either be left out or set to some higher value. Devices such as the AppleTV and the iPhone appear to be able to handle up to 2500 Kbps.

If VBR is chosen and iPod compatibility is turned on, this parameter should be set to 1450 instead of 768. As of Firmware 1.1, iPod (video) systems can handle H.264 video bursting up to 1500 Kbps. Extensive testing done in the course of developing HandBrake? (which uses the same underlying libraries as nuvexport) shows that setting this value to "1500" can still result in small local peaks over 1500 and, therefore, result in skipping during video playback. Therefore, 1450Kbps is a safer choice.

I suspect that 768 is in this codebase because the original firmware available for iPod (video) systems released back in 2005 did have a 768Kbps cap on H.264 video. Those systems should have had free firmware upgrades applied by now, and iPod family devices capable of video playback which have been released since then share the 1500Kbps limit.

http://handbrake.m0k.org/trac/wiki/BuiltInPresets#iPod shows the current best practice for iPod (video) x264 options (albeit in mencoder format).

Change History (1)

comment:1 Changed 12 years ago by xris

Resolution: fixed
Status: newclosed

(In [14998]) Update for better ipod bitrate settings now that ipods themselves have better supported formats. Also change the me_method to match Handbrake's preferred format, since I trust their settings. Closes #3934

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