What is an IDR?
IDR stands for Instantaneous Decoder Refresh. IDR frames are a specific type of keyframe used in video compression standards like H.264 (AVC) or H.265 (HEVC). IDR frames serve as reset points for the decoder, allowing for error resilience and efficient random access within the video stream.
Here are the key characteristics of IDR frames:
Self-Contained Keyframes: Similar to regular keyframes (I-frames), IDR frames are complete and self-contained frames that do not rely on any other frames for decoding. They contain all the necessary information to represent a full frame of video.
Resetting the Decoder: When an IDR frame is encountered during decoding, the decoder discards any previously stored reference frames and starts decoding from that point onwards. This resetting of the decoder's reference frame buffer ensures that any errors or artifacts that may have accumulated in the reference frames are eliminated, preventing error propagation throughout the video stream.
Enhanced Error Resilience: IDR frames play a crucial role in error resilience during video streaming. If errors occur during transmission, subsequent frames can be affected. However, with IDR frames strategically placed in the video stream, the decoder can recover more easily from errors since it can reset to a clean reference frame.
Random Access Points: IDR frames facilitate efficient random access within the video stream. Users can seek directly to an IDR frame without the need to traverse and decode all preceding frames. This is particularly important for seeking to different parts of the video or starting playback at specific timestamps.
The insertion of IDR frames at regular intervals is important for maintaining video quality, error resilience, and enabling random access. The frequency of IDR frames in the video stream can vary based on encoding settings, streaming protocols, and the desired balance between video quality and efficient decoding.
In summary, IDR frames (Instantaneous Decoder Refresh frames) are keyframes used in video compression standards. They serve as reset points for the decoder, allowing for error resilience, efficient random access, and improved video stream reliability. IDR frames play a crucial role in maintaining video quality and facilitating seamless playback in streaming applications.