I-frame size estimation based on edge strength
View Patent ↗Various embodiments of the present invention relate to systems, devices and method of video encoding that select a quantization parameter set based on a global edge strength value and an available bitrate for a corresponding compressed frame. Quantization parameters are selected using a mathematical correlation between the global edge strength value of the I-frame and an available bitrate/maxim target frame size for the corresponding compressed frame.
1. A video encoding system comprising
a reference decoder comprising at least one buffer to constrain bitstream data by setting an available bitrate based on an amount of data stored within the at least one buffer;
a rate quantization model module, coupled to receive the available bitrate and a global edge strength value of an intra-coded video frame (I-frame) indicative of the magnitude of edges within the I-frame, the rate quantization model module selects a preferred set of quantization parameters for the video frame from a plurality of sets of quantization parameters based on the available bitrate and the global edge strength value only, said selection is made only on a frame basis;
a video encoder, coupled to receive the preferred set of quantization parameters, the video encoder performs a quantization operation in accordance with the preferred set of quantization parameters during an encoding procedure of the I-frame.
2. The video encoding system of claim 1 further comprising a preprocessor, coupled to communicate with the rate quantization model module, the preprocessor generates the global edge strength value during preprocessing of the I-frame.
3. The video encoding system of claim 2 wherein the global edge strength value is generated using a Sobel Edge Strength analysis of the I-frame.
4. The video encoding system of claim 1 wherein the video encoder operates in accordance with the H.264 international video codec standard.
5. The video encoding system of claim 1 wherein the rate quantization model module employs a sequential search to select the preferred set of quantization parameters from a plurality of sets of quantization parameters.
6. The video encoding system of claim 1 wherein the rate quantization model module employs an iterative search to select the preferred set of quantization parameters from a plurality of sets of quantization parameters.
7. The video encoding system of claim 1 wherein the rate quantization model module comprises:
a frame size interface on which an available bitrate is received;
an edge strength interface on which a global edge strength value is received; and
a quantization parameter processor, coupled to receive the available bitrate and the global edge strength value, the quantization parameter processor selecting the preferred set of quantization parameters based on the available bitrate and the global edge strength value.
8. The video encoding system of claim 7 wherein the rate quantization model module further comprises a memory, coupled to the quantization parameter processor, the memory stores a plurality of sets of quantization parameters.
9. The video encoding system of claim 8 wherein the preferred set of quantization parameters is selected from the plurality of sets of quantization parameters.
10. A method for encoding an I-frame, the method comprising:
receiving an available bitrate;
receiving a global edge strength value indicative of the magnitude of edges within the I-frame;
selecting a preferred set of quantization parameters from a plurality of sets of quantization parameters based on an analysis of the available bit rate and the global edge strength value only, said selection is made only on a frame basis; and
performing a quantization process on at least one block within the I-frame in accordance with the preferred set of quantization parameters.
11. The method of claim 10 further comprising the step of generating the global edge strength value during a preprocessing operation on the I-frame.
12. The method of claim 11 wherein the global edge strength value is generated using Sobel Edge Strength analysis.
13. The method of claim 10 wherein the I-frame is encoded in accordance with H.264 standard.
14. The method of claim 10 wherein a sequential search is used to select the preferred set of quantization parameters from the plurality of sets of quantization parameters.
15. The method of claim 10 wherein an iterative search is used to select the preferred set of quantization parameters from the plurality of sets of quantization parameters.
16. The method of claim 10 wherein the available bitrate is received from a reference decoder and relates to a maximum allowable frame size.
17. A rate quantization processor comprising:
a frame size interface on which an available bitrate is received;
an edge strength interface on which a global edge strength value, indicative of the magnitude of edges within the I-frame, is received; and
a quantization parameter processor, coupled to receive the available bitrate and the global edge strength value, the quantization parameter processor selecting the preferred set of quantization parameters based on the available bitrate and the global edge strength value only, said selection is made only on a frame basis.
18. The processor of claim 17 wherein the rate quantization module further comprises a memory, coupled to the quantization parameter processor, the memory stores a plurality of sets of quantization parameters.
19. The processor of claim 17 wherein the edge strength interface further receives a faint edges value indicative of faint edges being present within the I-frame.
20. The processor of claim 17 wherein the faint edges value indicates that compensation is to be performed to account for faint edges within the I-frame.
21. The system of claim 1 , wherein the I-frame includes multiple macroblocks, and the global edge strength value is based on an average edge strength magnitude value of the multiple macroblocks comprising the I-frame.
22. The system of claim 21 , wherein the global edge strength value of the I-frame is the sum of the average edge strength value of the multiple macroblocks in the I-frame.
23. The system of claim 5 , wherein the sequential search for the preferred set of quantization parameters comprises setting an initial frame size and determining a quantization parameter corresponding to the initial frame size, and determining a difference of frame size relative to a target frame size, and sequentially calculating differences of frame size for successive values of all quantization parameters relative to the target frame size, and the preferred set of quantization parameters corresponds to the quantization parameters providing a smallest minimal difference of frame size relative to the target frame size.
24. The system of claim 6 , wherein the iterative search for the preferred set of quantization parameters comprises comparing a first calculated frame size of a first indexed quantization parameter with a second calculated frame size of a second indexed quantization parameter in pairs, iteratively setting a new boundary index resulting from the comparison of calculated frame sizes using the first and second indexed quantization parameters, iteratively comparing calculated frame size in relation to a frame size calculation using quantization parameters corresponding to the new boundary index and selecting one of the indexed quantization parameters as an optimal indexed value depending on the calculated frame sizes, as the preferred set of quantization parameters.