Subsections
Extra “cin_” Options for Render with FFmpeg
There are several special parameters that can be used in the ffmpeg
options file to pass values to the codecs that are not normally
available. They're called Global Options. These are explained
below.
The Render menus allows you to choose the
codec input pixel format (figure 7.4). The Pixels
selection provides the available pixel format options for the chosen
codec type; valid choices vary for the different file types. This
list represents the formats that the codec advertises. It is not
always complete, and it may include options that are not legal with
all parameter configurations.
Figure 7.4:
Render & Video Preset menus displaying Pixel choices
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- The Bitrate, Quality, and Pixels
fields are only updated when the Video Options are reloaded. This
occurs when you either change the ffmpeg file format, or video
presets compression fields.
- If the video options preset has cin_pix_fmt
defined, its value will be loaded as the default. If you override
the default, the value you specify will be used.
- If the video options preset does not have
cin_pix_fmt, the default pixel format will be computed by
ffmpeg (avcodec_find_best_pix_fmt_of_list), using the
session format as the source choice. The best is usually
the format which is most similar in color and depth.
- If no choices are available, yuv420p for video will be used.
- You can also specify ffmpeg pixel formats which are not in the
list. The list is provided by ffmpeg as input selection, but is
more like suggestions than fact. For example, the raw formats can
take almost any format, but the rawvideo codec actually specifies no
legal formats. Note that if you want a very specific Bitrate you must
make sure there is not conflicting parameter values set such as Quality
or CRF.
Some option files provide cin_pix_fmt to
suggest a choice for good quality output or to prevent parameter
errors when the other provided parameters conflict with the
best pixel format. This is the case in
faststart_h264.mp4 where the profile=high
parameter dictates pixel format must be yuv420p.
If you specify the bitrate, you can not
specify the quality or CRF.
Example: cin_bitrate=2000000
If you specify the quality, you can not
specify the bitrate.
Example: cin_quality=7
This parameter is useful for 2 pass
operations.
Example: cin_stats_filename
/tmp/cin_video_vp9_webm
For audio the preset sample format
default is computed in a similar way as stated above for video or
can be set with the cin_sample_fmt parameter
(figure 7.5). If no choices are provided, s16 will be
used.
Example: cin_sample_fmt=s16
Figure 7.5:
Render menu showing where Samples is
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(muxers). In the window of the
wrench in addition to the View button, which
allows more global options and changes to the formats, there is an
additional Format button that allows you to modify the
Private Options, i.e. relating to specific muxing formats. More
information on all these options can be found at
ffmpeg.org
sections 19 and 21. See also Modifying FFmpeg Format Options inside CINELERRA-GG.
Render presets in CINELERRA-GG should work Out Of the Box. You can still configure the Global Options and Private Options manually. Finding the combination of parameters that best suits your needs, or simply finding working (legal) combinations, requires studying each codec in depth. You can start by looking in Wikipedia until you get to download and study the white papers of the codecs of interest. In any case, you must then start a long experimental phase, trying presets with different configurations or creating new ones, until you get satisfactory results. If you create new presets it is a good idea to make them known on the mailing list (https://lists.cinelerra-gg.org/mailman/listinfo/cin) or on the MantisBT Bug Tracker (https://www.cinelerra-gg.org/bugtracker/my_view_page.php) so that they can be integrated into subsequent versions of CINELERRA-GG. For an introduction see Overview on Formats and Codecs.
The CINELERRA-GG Community, 2021
https://www.cinelerra-gg.org
