GOP Group Of Pictures GOPs For Encoded Video Stream

group of pictures


When the things comes in terms of Encoding , Decoding ,Streaming and Compression then we gets in touch of term GOP. If you are in Streaming Media line then it is very important for us to know about GOP. Because GOP plays very important role in Streaming Media.

So in this article we will cover What is GOP and How GOP works , GOP Structure and its basic concepts.

What Is GOP

GOP stands for Group Of Pictures. GOP defines how the order of Inter-frames and Intra-frames are arranged. Coded video stream contains the GOPs. These GOPs are known as Successive GOPs. Successive GOPs are used to generate visible frames.

If you are watching TV channels or watching videos on Youtube then all of these videos are compressed and streamed. In case you are watching these videos on 30 Frame Per Second. Then it doesn’t mean you are seeing full 30 pitchers. Instead of that you are seeing Group Of Picture. This GOP is divided into three frames as I-Frame , P-Frame and B-Frame.

group of pictures


I-Frames stands for Inter-Frames.  I-Frames are having the images in compressed form. Group Of Picture starts with I-Frame only. As you can see in figure.


P-Frames stands for Predicted-Frames. P-Frames represents the past frames only. It is not a full complete image.


B-Frames stands for Bidirectionally Predicted-Frames. B-Frames represents past and future frames. It is also not a complete image.

Thus Group Of Pictures is combined form of I-Frames , P-Frames and B-Frames.

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Working Of Group Of Pictures

To understand the working of GOP we need to have a example of recording studio.

In a recording studio a new reader is reading the news. Recording camera is mounted on tripod so camera so recording is stable from camera side. Now background picture of recording studio is still. While news reader is only the object moving. In this situation I-Frame is same because it represents background of studio that is not changing. So I-Frame is known as reference frame.

While news reader is moving, which represents B-Frames and P-Frames.


As discussed above GOP is known as Group Of Pictures found in encoded video stream. Successive pictures makes the  Gops. GOPs are composed of three frames I-Frames , P-Frames and B-Frames. Where I-Frames are reference frames denotes the still images while other P-Frames and B-Frames denotes moving objects or motion.

Know More About Difference Between MPEG 1 MPEG 2 MPEG 4

Reference : apple docs

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