VCU End-to-End Latency - 2023.1 English

H.264/H.265 Video Codec Unit v1.2 Solutions LogiCORE IP Product Guide (PG252)
Document ID
PG252
Release Date
2023-05-16
Version
2023.1 English

The following table shows the latency for the VCU pipeline stages.

Table 1. VCU End-to-End Latency
Use Case 5 Capture Encode (HEVC / AVC) Decode Display
Normal Latency 16.6 ms 18 ms / 35 ms 200 ms 16.6 ms
Reduced Latency 16.6 ms 18 ms / 35 ms 50 ms 16.6 ms
Low Latency 16.6 ms 4 ms / 10 ms 17 ms 16.6 ms
Xilinx Low-Latency 3, 4 1 ms 4 ms / 10 ms 9 ms 16.6 ms
  1. The values in the above table are estimated numbers for 4kp60.
  2. In case of normal latency, the decode reported latency is calculated according to the below formula. The DPB size here is depends on profile and level reported latency = DPB size + internal entropy buffers + reconstruction buffers + concealment buffers.
  3. Xilinx low-latency is achieved using Sync IP. For more information, see VCU Sync IP v1.0.
  4. Xilinx low-latency supports 25 Mb/s for single stream of 2160p60 and 6 Mb/s for four streams of 1080p60.
  5. The exact worst case latencies depend upon the input content and system load. Latency numbers mentioned in this table correspond to the theoretical latencies reported by the respective elements. The latencies of elements should stay under the reported ones.

Latency Numbers

Latency numbers are derived from the following equations:

Table 2. Latency Numbers
Use Case Equation 1 Latency
v4l2src 1 frame period for the capture buffer 16.66 ms
omxh265enc (HEVC encoder) 1 frame period for input capture buffer rounded to ms + 1 ms margin = 17 ms + 1 ms 18 ms
omxh264enc (AVC encoder) 1 frame period for input capture buffer rounded to ms + 1 intermediate buffer + 1 ms margin = 17 ms + 17 ms + 1 ms 35 ms
Normal Latency [omxh265dec & omxh264dec (AVC/HEVC Decoder)] DPB size (5 for default level i.e. 5.2) + internal entropy buffers (default=5) + reconstruction buffers (default=1)+ concealment buffers (default=1) = 12 *16.66 ms 200 ms
Reduced Latency 1 frame period to insert frame into decoder + 1 frame period to decode + 1 frame period margin = 16.6 ms + 16.6 ms + 16.6 ms 50 ms
  1. All the equations in this table have been calculated for 60 fps video.