Render Profile Parameters Explained

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Kdenlive now makes use of property presets delivered by the melt project (see MLT Presets). These presets are referenced by the properties=<preset> syntax. In the example illustrated, the render profile is referencing lossless/H.264. This refers to a property preset found in file H.264 found on the system at

Okna:

C:\Program Files\kdenlive\share\mlt\presets\consumer\avformat\lossless

Linux:

/usr/share/mlt/presets/consumer/avformat/lossless

On a default install, all the <presets> referenced in the render settings in Kdenlive will be referring to presets found in

Okna:

C:\Program Files\kdenlive\share\mlt\presets\consumer\avformat\

Linux:

/usr/share/mlt/presets/consumer/avformat/

You reference presets found in subdirectories of this folder using a <subdirname>/<profile> syntax as shown in the example above.

properties=lossless/H.264
g=120
crf=%quality
ab=%audiobitrate+'k'

The preset files found at /usr/share/mlt/presets/consumer/avformat/ and C:\Program Files\kdenlive\share\mlt\presets\consumer\avformat\, respectively, are simple text files that contain the melt parameters that define the rendering. An example is shown below. These are the same parameters that were used in earlier versions of Kdenlive.

Contents of lossless/H.264:

f=mp4
acodec=aac
ab=384k
vcodec=libx264
intra=1
vb=0
g=0
bf=0
preset=medium
qscale=1
qp=0
coder=ac

<!--T:28-->
meta.preset.extension=mp4
meta.preset.note=Intra-frame only, lossless compressed MPEG-4 AVC with AAC audio

Jak je číst

Essentially, the parameters are instructions for ffmpeg which is used for encoding the video and audio streams. Hence it should not come as a surprise that the parameters are well documented by the ffmpeg project.

In the example above the parameters are:

f=mp4
acodec=aac
ab=384k
vcodec=libx264
intra=1
vb=0
g=0
bf=0
preset=medium
qscale=1
qp=0
coder=ac

Another example for DVD output:

f=dvd
vcodec=mpeg2video
acodec=mp2
b=5000k
maxrate=8000k
minrate=0
bufsize=1835008
mux_packet_s=2048
mux_rate=10080000
ab=192k
ar=48000
s=720x576
g=15
me_range=63
trellis=1
profile=dv_pal_wide
pass=2

Looking up the ffmpeg options translates these parameters as follows:

Main option is:

-f fmt            force format

Video options are:

-vcodec codec     force video codec ('copy' to copy stream)
-pass n           select the pass number (1 or 2)
-b bitrate        set bitrate (in bits/s)
-vb bitrate       set video bitrate (in bits/s)
-s size           set frame size (WxH or abbreviation)
-me_range         limit motion vectors range (1023 for DivX player)
-trellis          rate-distortion optimal quantization

Audio options are:

-acodec codec     force audio codec ('copy' to copy stream)
-ab bitrate       set audio bitrate (in bits/s)
-ar rate          set audio sampling rate (in Hz)

The AVCodecContext AVOptions include:

-b                set bitrate (in bits/s)
-maxrate          set max video bitrate tolerance (in bits/s)
-minrate          set min video bitrate tolerance (in bits/s)
-g                set the group of picture size

All the render profile options are documented in the ffmpeg documentation.

See also MLT Presets for more details on the MLT preset property.