The difference between the I frame and IDR frame in H264

DR (instantaneous decoding refresh)--instant decode refresh.

Both I and IDR frames are predicted using intra-frame. They are all the same thing , in the encoding and decoding for convenience, the first I-frame and other I-frame differences, so the first I frame is called IDR, so it is convenient to control the encoding and decoding process. the function of the IDR frame is to refresh immediately so that the error does not propagate, starting with the IDR frame and re-calculating a new sequence to begin coding . While I-frames do not have the ability to randomly access, this feature is assumed by IDR. IDR can cause DPB ( Decodedpicturebuffer Reference Frame list-This is the key to emptying, and I will not . The IDR image must be an I image, but the I image is not necessarily an IDR image . A sequence can have a lot of I images, I image after the image can refer to I image between the image to do motion reference. There can be a lot of I images in a sequence, and the image after I image can refer to the images between I images for motion reference.
for IDR frames, all frames after the IDR frame cannot reference the contents of the frame before any IDR frames , and in contrast, for normal I-frames, the B-and P-frames after them can refer to the I-frame before the normal I-frame. From a randomly accessed video stream, the player can always play from an IDR frame , since there is no frame after it referencing the frame before it. However, you cannot start from any point in a video that does not have an IDR frame, because the frame that follows will always refer to the previous frame.



Description: This article is from the network collation