Scalable MPEG video/macro block rate control
View Patent ↗A scaleable macro block rate control method particularly well-suited for MPEG video. There is provided a method to easily derive a quantization parameter (QP) value using information such as bit usage, previous QP values and SAD values from the past encoded and future frames. The method utilizes quantization estimation techniques based on statistical relationships between different intensity measures, such as distortion intensity, absolute difference intensity and mean of absolute difference intensity. The method is well-suited to applications utilizing MPEG video such as MPEG-1, MPEG-2, MPEG-4, JVT/H.264 standards and so forth.
1. A method for scalable rate control for MPEG video, comprising:
calculating an average bit count using a plurality of future frames;
calculating a previous bit count using a past encoded frame;
calculating a target Qscale using the average bit count and previous bit count to adjust a deficit/surplus bit rate budget;
refining Qscale using SAD statistics from past encoded frames and current buffer status; and
bounding Qscale in the range of pre-defined MinQP and MaxQP values.
2. A method as recited in claim 1 , wherein said MinQP value is selected for maintaining maximum video quality for encoding a video sequence.
3. A method as recited in claim 1 , wherein said Qscale value is a function of bit rate and frame rate.
4. A method as recited in claim 1 , further comprising:
adjusting a bit rate budget;
estimating a target bit rate for a current frame;
computing a Qscale value for first and subsequent I-VOPs; and
computing a Qscale value for P-VOPs.
5. A method as recited in claim 4 , wherein said step of adjusting a bit rate budget comprises:
allocating bits as a function of SAD values of P-VOP and MAD values of I-VOP by calculating total available bit budget in a RC window and bit budget for a frame before encoding a frame.
6. A method as recited in claim 4 , wherein target bit rate estimation comprises:
determining bit allocation for a frame by frame type and the associated SAD/MAD.
7. A method as recited in claim 6 , wherein for each picture type, all of its associated SAD/MAD values are summed, and the bit rate budget for a frame with P-type is proportional to its MAD with respect to overall MAD within a RC sliding window.
8. A method as recited in claim 1 , further comprising encoding a video frame or object using QP obtained in a pre-encoding step if either frame- or object-level rate control can be activated.