Arithmetic coding procedure as a flow diagram

We will now try to present the steps of the arithmetic coding procedure as a flow diagram. Let the alphabet of the message to be transmitted consist of the character set {xi}(in the examples above, this alphabet consisted of three characters, {a, b, EOF}, with i = 1 for a, i = 2 for b, and i = 3 for EOF). Construct an array of values

, where fi is the relative frequency of the i-th character in the message. Let P0 = 0 and PN = 1, where N is the number of characters in the alphabet. (Again, in the coding example discussed above, we have N=3 and P = {0, 0.1, 0.95, 1}.) Using the notation thus introduced, the steps to be performed during arithmetic coding of each character can be presented as a flow diagram shown in Fig. …

The task most operators face today is how to keep the subscriber base loyal. Stable high quality of broadcasting is one of the factors that helps address this challenge. To maintain high quality and detect violations in the stream, it is important to track various parameters.

All monitored parameters are divided into two types: relating to Quality of Service (QoS) and Quality of Experience (QoE). In this article, we will consider QoS parameters that are most important for OTT/IPTV content delivery.

No signal (BadSource) error is the most critical parameter displaying the “red” state of the network delivery. This state occurs when the monitoring system cannot receive data for further analysis for some reason. To address the No signal error, it is required to investigate the cause of the issue and promptly define its location: streamer, switching equipment or network. This problem can be solved by using several analyzing solutions or multiple clients (probes) within the frame of a distributed monitoring system. …

Arithmetic coder basics and intro to binary arithmetic coder

Let us recapitulate the main steps of processing a video frame as it is being encoded using a H.265/HEVC system (Fig. 1). At the first step, termed conventionally “block division”, the frame is divided into blocks called CUs (Coding Units). The second step involves predicting the image inside each block using spatial (Intra) or temporal (Inter) prediction. When temporal prediction is being performed, a CU block can be divided into sub-blocks called PUs (Prediction Units), each of which can have its own motion vector. The predicted sample values are then subtracted from the sample values of the image being coded. A two-dimensional (2D) difference signal, or Residual signal, is formed for each CU as a result. …

Low broadcast latency has become a mandatory requirement in any tenders and competitions for building of head-end stations and CDNs. Previously, such criteria were applied only to sports broadcasting, but now operators require low latency from broadcast equipment suppliers for every sphere: broadcasting news, concerts, performances, interviews, talk shows, debates, e-sports and gambling.

Latency in general terms is the time difference between the time when a particular video frame is captured by a device (camera, playout, encoder, etc.) and the time when this frame is played on the display of an end user.

Low latency should not reduce quality of signal transmission, which means that minimal buffering is needed when encoding and multiplexing while maintaining a smooth and clear picture on the screen of any device. Another prerequisite is guaranteed delivery: all lost packets should be recovered and transmission on open networks should not cause any problems. …

The HEVC standard implements all of the above ideas that provide the best inter-frame prediction “quality”. This involves the ability to specify the prediction vector with 1/4-pixel accuracy, use one- and bi-directional prediction, vary adaptively the shape and size of the image areas being predicted, create long (up to 15 elements) reference frame lists, and use motion vector prediction algorithms so that only information about the difference vectors (mvd) is added to the encoded stream. How is this all implemented? Let’s find out.

Reference image information

It is clear that to implement inter-prediction, the encoding and decoding systems must have a memory buffer to store the decoded images. This buffer is called a DPB (from Decoded Picture Buffer). Some images in DPB are “waiting” for their turn to be displayed on the screen (in the decoding system), while others stay in the buffer to enable inter-prediction when coding other video frames. The frames that are going to be used for inter-prediction have to be tagged in some way during coding, and the information about these tags must be added to the encoded video stream. There are two types of such tags in HEVC. The first is called short-term reference. It is used to tag those images in the DPB that can be used as inter-prediction reference frames for blocks in the current frame or in the two closest subsequent video frames (in the order of decoding). The second type of tag, called long-term reference, concerns those frames in DPB that can be used to predict image blocks in frames that are more than two frames away from the current one (again, in the order of decoding). All images in the DPB that are not tagged as short-term reference or long-term reference are considered unused for reference and cannot be used at a later time to perform inter-prediction. The information about these tags is added to the header of each frame in the encoded video stream. …

Elecard CodecWorks is designed for video compression based either on CPU or Intel GPU. In this video we review the advantages of CPU and GPU use. To test the demo version of CodecWorks, go to: https://is.gd/cKxYng

In this video:
00:23 CPU or Intel GPU transcoding
00:51 Hardware recommendations for CPU transcoding
00:57 Hardware recommendations for GPU transcoding
01:10 Advantages of CPU use
01:38 Advantages of GPU use
02:25 Comparing expenses on servers for a standard ОТТ transcoding scheme

Possible ways of eliminating temporal or spatial redundancy in video images. Block-by-block basis of image processing in HEVC. The procedure of spatial prediction: four major steps. Algorithms of calculation of the pixel values inside the block being coded.

Video coding systems implementing the HEVC standard are categorized as so-called hybrid block-based codecs. “Block-based” means here that each video frame is divided during the coding process into blocks to which the compression algorithms are then applied. So what does “hybrid” mean? To a large extent, the compression of video data during coding is achieved by eliminating redundant information from the video image sequence. Obviously, the images in the video frames that are adjacent in time are highly likely to appear similar to one another. To eliminate temporal redundancy, the previously coded frames are searched for the most similar image to each block to be coded in the current frame. Once found, this image is used as an estimate (prediction) for the video frame area being coded. The prediction is subtracted from the pixel values of the current block. In the case of a “good” prediction, the difference (residual) signal contains significantly less information than the original image, which provides efficient compression. However, this is just one way of eliminating redundancy. HEVC offers another option where the pixel values from the same video frame as the current block are used for prediction. This kind of prediction is called spatial or intra-frame prediction (Intra). Thus, what the term “hybrid” refers to is the use of the two possible ways of eliminating temporal or spatial redundancy in video images at the same time. It should also be noted that intra-prediction efficiency is what determines in large measure the efficiency of the coding system as a whole. …

Today we want to share the success story of how we took part in the large-scale project on content preparation and broadcasting of 12 channels in the Moscow underground trains.

The Moscow Metro is the backbone of the Moscow transport system. It consists of 15 lines and 269 stations, on which more than 12 thousand trains are passed daily. There are 6200 video screens installed in the subway cars, which broadcast TV channels, information videos, and commercials. The monitors are designed for a large audience: more than 7 million people use the metro every day.

Task

Preparation and broadcasting of 12 TV channels together with advertising content in Moscow Metro trains. Announcements and alerts should be inserted into broadcast. …