Description

Modify H264, H265 and MPEG4 encoding behavior.

typedef struct {
  u32 targetBitRate;
  u8 intraFrameInterval;
  u8 lfDisableIdc;
  u8 airMbPeriod;
  u8 sliceRefreshRowNumber;
  u8 flags;
  u16 displayId;
} SLASetH264Parameters_t;

SightLine's H264 (AVC), H265 (HEVC) and MPEG4 compression encodes the video stream into I-frames and P-frames. I-Frames are a compression of the entire video frame, while P-Frames only include the delta between the video frame that was compressed in the last I-frame and the current video frame.
H264 and H265 compression can also use Intra Refresh mode to put blocks of I data in every frame.

See also: SLASetEthernetDisplayParameters_t to set the receiver IP address.; SLASetKlvData_t to set KLV metadata.; SLASetEthernetVideoParameters_t to change Down Sample and Frame Step.; SLAStreamingControl_t for starting and stopping video.; EAN-Encoding.pdf for additional details on SightLine Ethernet encoding.

Message ID 0x23

Byte Offset

Name

Description

4-7

targetBitRate

Target bit rate, bits per second (3000/1500: default 1500000, 17XX/4000: default 3000000). Actual bit rate will vary (see flags below).
NOTE: Maximum bitrates are:
17XX/4000 - 30 Mbps
3000 - 20 Mbps
1500 - 10 Mpbs

8

intraFrameInterval

1-90 = Intra Frame (I-frame) interval (default 30). The rate at which I-frames are produced.
0 = Intra Refresh mode where there are blocks of I data in every frame resulting in a smoother overall bitrate.
NOTE: Not all decoders can connect to an intra refresh stream. Intra refresh is only support with H264 on the 17XX/3000/4000, and H265 on the 17XX/4000.

9

lfDisableIdc

H264 in-loop filter control

Bits	Description
0-3	0 = filter all edges (default), 1 = disable all filtering, 2 = disable slice edge filter, other values = Reserved
4-6	Reserved set to 0
7	0 = default, 1 = apply encoder fix to support hardware decoders (1500 only)

10

airMbPeriod

Only used if intraFrameInterval is 0 (Intra Refresh mode)
1500 - Not available
3000 - Adaptive Intra Refresh (AIR) mega-block period (default 0)
17XX/4000 - Cyclic Intra Refresh (CIR) mega-block period, if 0 a default value of 20 will be used

11

sliceRefreshRowNumber

Only used if intraFrameInterval is 0 (Intra Refresh mode)
1500 - Not available
3000 - Slice refresh row number – number of rows coded as each intra slice (default 0)
17XX/4000 - Not available

12

flags

Bits

Description

0-1

Profile (H.264 17XX/3000/4000 only, set to 0 otherwise)

0	Baseline profile (default 1500/3000)
1	Main profile
2	High profile (default 17XX/4000)

2-3

Reserved set to 0

4-5

Bit Rate Mode (H.264/H.265 only, set to 0 otherwise)

0	Legacy (default 1500/3000). Approximates Variable Bit Rate (VBR) with loose constraints but a fairly short time constant.
1	Variable Bit Rate (VBR) (default 17XX/4000). Bit rate dynamically changes based on the video content and motion in order to acheive high quality video. (Added to 1500 in 3.4)
2	Constrained Bit Rate Mode. Encoder parameters are tuned to achieve approximate target bit rate. (Not available on 1500/17XX/4000, on 17XX/4000 try Intra Refresh mode)

6-7

Reserved set to 0

13-14

displayId

Network Display ID
3000 / 4000: (0x0002 = Net0, 0x0080 = Net1, 0x0082 = both)
17XX: (0x0002 = Net0)
1500: Ignored or 0x0000