API Reference
4-18
Field Datatype
Input/
Output
Description
forceFrame
XDAS_Int32
Input
Force the current (immediate) frame to be
encoded as a specific frame type.
Supports only
IVIDEO_NA_FRAME
,
IVIDEO_I_FRAME
and
IVIDEO_IDR_FRAME
frame types.
See
IVIDEO_FrameType
enumeration for
details
Default:
IVIDEO_NA_FRAME
interFrameInterval XDAS_Int32
Input
Number of B frames between two reference
frames; that is, the number of B frames between
two P frames or I/P frames.
Not supported in this version of H264 Encoder.
Default: 0
mbDataFlag
XDAS_Int32
Input
Flag to indicate that the algorithm should use MB
data supplied in additional buffer within
inBufs
.
Not supported in this version of H264 Encoder.
Default: 0
Note:
The following are the limitations on the parameters of
IVIDENC1_DynamicParams
data structure:
inputHeight <= maxHeight
inputWidth <= maxWidth
refFrameRate <= maxFrameRate
targetFrameRate <= maxFrameRate
targetBitRate <= maxBitRate
The rate control used in H.264 Encoder can work for a target bit-rate of a
minimum of 32 kbps and a maximum of 10 mbps up to level 3. However,
the recommended range varies with the format. For example, for NTSC
D1, the recommended range is 1.5 mbps to 6.0 mbps.
The bit-rate achieved by the encoder may deviate largely from
the
value
specified by the
targetBitRate
field of the
IVIDENC1_DynamicParams
data structure when the content is
highly static and the
bitrate
is high.
The
targetFrameRate
and
refFrameRate
should be equal as
frame rate up-conversion and down-conversion is not
supported/used.
The rate control presets
IVIDEO_LOW_DELAY
/IVIDEO_LOW_STORAGE
takes at least 1-2 seconds for the rate
control algorithm to stabilize the target bit-rate.
For resolutions whose
inputWidth
is not a multiple of 32, the
encoder internally rounds the
inputWidth
to the next multiple of
32. The encoder internally pads along the width of the image to
make it a multiple of 32. In the bit-stream the frame cropping flags
are set by the encoder to not display the padded pixels. The
application should have allocated an input buffer enough to perform
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