#11292: AMD Hardware Encoding is Broken in versions >= 7.1
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Reporter: TanMan | Owner: (none)
Type: defect | Status: open
Priority: important | Component: avcodec
Version: git-master | Resolution:
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by Roman):
1. The correct command line is expect to be:
`ffmpeg.exe -i input.mp4 -c:v h264_amf -b:v 1M -max_rate 1.6M out.mp4`
2. If the command line is without `-max_rate`, then there is a warning
message “rate control mode is `PEAK_CONSTRAINED_VBR`, but rc_max_rate is
not set”. The encoding will still work normally, and the default max_rate
of 1.5x (1.5 * bitrate) will be applied.
`ffmpeg.exe -i input.mp4 -c:v h264_amf -b:v 1M out.mp4`
3. If the command line is without `-b:v 1M`, then a default bitrate of
20Mbps will be applied.
`ffmpeg.exe -i input.mp4 -c:v h264_amf out.mp4`
4. Considering the reported case plus `-maxrate`,
`ffmpeg -i input -c:v hevc_amf -maxrate 2000k output`
Since the command line does not specify the bitrate `-b:v`, then the
default bitrate of 20M will be applied by AMF.
Since the `-maxrate 2000k` is smaller than the default bitrate of 20M,
then the `-maxrate 2000k` will be ignored and won’t take effect.
As a result, a large file will be produced where the actual bitrate is
20M.
A patch will be submitted to remove the warning message “rate control mode
is `PEAK_CONSTRAINED_VBR`, but rc_max_rate is not set”. It brought a
little confusion.
For the bitrate parameter `-b:v`, we previously set it to 2M in FFmpeg,
but it has now been changed to -1. In AMF, the default value is 20M. This
explains the difference seen between past and present behavior.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/11292#comment:6>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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