[Photos] About the application of hard disk technology in slow motion production[Copy link]
[Photos and text] On the application of hard disk technology in slow motion production July 26, 2006 9:43 Source: World Radio and Television
Author: Mr. Sheng Xiaohui, video engineer of the Technical Operations Center of Shanghai Media Group.
Keywords: slow motion video server
In recent years, Shanghai's active cooperation with various sports events around the world, such as F1, V8 Touring Car Race, NBA pre-season, Tennis Masters Cup, World Table Tennis Championships, etc., has enabled us to develop broadcasting ideas while realizing the important role of hard disk slow motion technology in broadcasting. It allows the audience to enjoy a more comprehensive and detailed picture, and even see the subtle emotional changes of coaches and players on both sides during the game, which greatly improves the sense of presence of sports broadcasting. This article focuses on how to make good use of slow motion technology in broadcasting. Slow Motion System
As we all know, the traditional slow motion system is based on a tape recorder, equipped with a remote control panel to achieve playback at different speeds. Many TV stations still have this equipment on their broadcast vehicles. This slow motion production method is simple to operate and the equipment is cheap, but it has a disadvantage, that is, it cannot be recorded during playback. The characteristics of sports games are that they change rapidly. If you miss the highlights during the playback process, it is undoubtedly a great regret for the audience. In addition, it requires rewinding time, the picture quality is not high when playing back at a lower speed, and the black field will be generated when the magnetic field is disconnected during broadcasting. These deficiencies restrict the improvement of slow motion quality. To solve these problems, some foreign manufacturers have developed slow motion systems based on hard disk technology. The more popular ones are Profile of Grass Valley (GVG), Forum of Orad and SLSM of EVS, each of which has its own strengths.
Profile Video Server
Profile XP, the new generation media platform of the Profile series, supports both standard definition and high definition. Its modular structure, expandable software, hardware, RAID storage and remote error detection facilitate the maintenance of the chassis structure, making it a video server with high scalability and upgrade performance in the industry.
The PVS1100 video server is optimized for applications such as news and sports production. It features support for DVCPRO, DVCPRO50, MPEG-2 4∶2∶2 I-frame and D10 formats at 50Mb/s. Configurations include 2, 4, 6 and 8 bidirectional channels, which can be reconfigured as needed, and all channels provide enhanced slow motion capabilities for flicker-free playback. In order to keep pace with the production process, the PVS1100 is internally configured with dual-channel SDTI, which can record compressed video from a tape recorder in real time at up to 4 times the speed. More than 50 Profile XP media platform application developers are licensed to develop software in all aspects. PVS1100 supports GVG's applications, including SNMP-based remote monitoring NetCentralTM software and Profile InSyncTM automatic mirroring software.
Although Profile is very stable and has good scalability, it is not a hard disk server specifically used for slow-motion production. It is not well considered in terms of third-party application development, its operability is not strong, and there are problems with high-speed support. There is no perfect slow-motion solution so far, and it is not very suitable for live sports programs.
Forum Video Server
Forum is a multi-channel slow motion video server, mainly composed of 2 parts: Forum server host and Elefant II management control unit. It has a total of 6 channels, 4 channels can be set to record or replay at the same time, and the input and output of the channel can be set through the internal router, providing users with great freedom. Due to the use of wavelet compression technology, Forum can provide amazing video playback quality, and the image quality will not change with the playback speed. Super slow motion includes audio configuration, and each channel has 4 audio channels recorded simultaneously with the video, and the audio is in an uncompressed format. It supports external Time-Code device connection and Sony BVW protocol, allowing the reset signal of the tape recorder to be seamlessly embedded and ensuring redundancy. Equipped with dual power supplies, Forum with different storage capacities can record continuously for 24 to 72 hours (compression ratio 4:1), and the standard recording time is 48 hours. In addition, connecting Forum with an external RAID5 unit can replace the built-in storage.
Figure 1 Example of connection between Elefant panel and host
Elefant II is the control panel for Forum, equipped with a precise and durable Jog/Shuttle wheel, and provides a VCR-like operation mode. Highlight clips and time points can be set with the press of a button, and the broadcast list can be edited quickly; playback can be performed at any speed, and the camera angle can be changed smoothly; using user-defined buttons, a large number of highlights can be quickly sorted according to different themes, and the play list can be edited quickly. Forum can be managed through the Elefant II control panel, or Windows-based software, such as Orad Cyber-Sport software, can be used to directly control Forum. The latter control method provides new effects for live broadcasts of sports events, such as drawing static or dynamic offside lines, measuring ball speed, marking the trajectory of the ball, and other applications.
Forum is an upgradeable hard disk slow motion system. When you need to record many cameras at the same time, you can cascade Forum and transmit data through the SDTI network.
Forum's strengths lie in its Cyber Graphic and CyberSport live text and graphics systems, which can insert 3D subtitles with special effects during slow motion production, and recently added the ability to insert 3D graphics on the court screen for commentary. Its disadvantages are: the connection between the Elefant panel and the host is relatively complicated; it only supports a few control protocols such as Sony BVW; editing highlights (PlayList) is relatively complicated; it does not support high speed; and its scalability is relatively poor.
EVS DVR
SLSM is an early slow motion hard disk recorder of EVS. Because it does not have an audio module, it is equipped with an EVS digital audio accessory connected to the host for remote control. The machine has good stability. Since it does not support SDTI network, this stand-alone mode is no longer suitable for broadcasting large-scale sports events.
To this end, EVS launched a new generation of products LSM-XT, which has 6 channels, supports 4∶2∶2 10b 270MHz SDI signal, can freely set input and output, 16-channel AES/EBU and 8-channel ANOLOG audio input/output ports, RAID3 array, supports SDTI network, and forms a Sport-Net network with MAXS, Airbox and other equipment, which is suitable for large-scale sports game broadcasts. The internal signal flow of LSM XT is shown in Figure 2:
Figure 2 EVS LSM XT
When LSM XT is recording, the digital video signal is input from the digital input board, encoded by the encoder, and then separated by the video disk array controller and recorded on the hard disk; playback is another path, and the process is the opposite of recording. The video disk array uses RAID3 technology (parallel transmission with parity code), using a dedicated disk E to store all the check data, and creating a stripe set in the remaining disks to disperse the data read and write operations. If a hard disk is damaged, the video disk array will use RAID3 technology to rebuild the lost data based on the check value and overwrite the lost information with the backup data.
EVS LSM-XT has a transmission rate of 270/540MB/s; allows editing of highlights sequences with wipe and deformation effects during instant playback; supports almost all interface protocols based on RS-422 control; can customize compression ratios to obtain corresponding image quality according to user needs; supports high speed and high definition by simply changing templates and making simple settings. The latest version of LSM-XT software provides enhanced functions for the complete live broadcast of football events: naming cameras in the settings menu - different from the traditional CAM A/B/C/D/E camera screen display names of LSM XT, now more relevant names can be given, such as Side Left, Side Right, Goal Left, Goal Right, etc. Three keywords can be given to each clip using the keyboard or LSM remote control, such as clip 111A with three keywords Ronaldo, Goal, Head; quality ratings can be added to each clip (0 to ***); and tags for archiving to the Xfile system can be added to clips directly on the remote control. With this related information, operators can sort clips according to specific strategies (local or all machines on the network). You can search by keyword, search by image quality, search for TC code, and display relevant clips of specific TC time code in all LSM on the network. Through powerful search function and network environment, it provides high-quality slow-motion replay images for directors.
Compared with similar products from other companies, EVS's hard disk recorders have many unique advantages. The slow motion system composed of EVS's SportNet and new IP Director is also relatively mature, making EVS's hard disk recorders the mainstream product for slow motion production.
Application of EVS slow motion technology in sports event broadcasting
LSM-XT as a stand-alone unit
As a stand-alone machine, the most commonly used function of EVS LSM-XT is its quick replay function. The operator must first be familiar with the competition and the rules of the game. Experienced people will keep hitting MARK at the key moments of the game. Using LAST CUE, you can easily find the key points at the first time and replay them with a little adjustment. If it is a highlight clip, you can mark the in and out points as a CLIP (material) to save or push it to the highlight machine for highlight replay. In this working mode, the more practical function is multi-angle continuous playback. For example, in the production of a goal in a football match, we set LSM-XT to 4-in 2-out, PGM/PVW mode, select SWITCH TO IN, lock 4 cameras at different angles, preferably in different scenes in the same half; hit the goal before shooting, and when replaying, PGM first plays a shot that reflects the overall tactical coordination (for example, named Side Left T), and PVW selects a shot that reflects personal skills and prepares it (named Goal Left); when Goal Left is selected, it automatically returns to the goal, and immediately press TAKE after PGM is played. Goal Left switches to PGM and automatically plays, and then another shot is selected as PVW, and so on. The switching method can be set to wipe or superimpose. The advantage of this method is that the goal scene can be replayed quickly and orderly. Of course, it does not have to be set to SWITCH TO IN. For example, when broadcasting a baseball game, the batting scene is often followed by the running scene without returning to the goal.
When two or more LMS-XTs form a SportNet network, slow motion production becomes more flexible. We can use one LMS-XT exclusively for producing game highlights, using a dedicated editor to improve efficiency; or we can use both LMS-XTs as ordinary slow motion production equipment, so that we can choose more camera channels.
In view of the explosiveness and intensity of sports competitions, people often use high-speed cameras to obtain better images. For example, in tennis games, the speed of athletes and tennis balls is relatively fast, and the object tailing phenomenon in ordinary slow-motion lenses is serious. If the speed is too slow, there will be discontinuous jumping. In response to different phenomena, we take different methods to solve them: first, all cameras used for slow-motion shooting are marked with DTL buttons to appropriately strengthen the outline; negotiate with the staff of the venue and increase the venue illumination appropriately with permission, so that the large-magnification lens can get enough light, so that the shutter speed of the camera can be increased to 120Hz; all high-speed shots are uniformly determined to be about 33% of the normal playback speed during playback. The high-speed camera itself picks up information at a field frequency of 150Hz. After calculation and motion compensation, even if the slow-motion playback is performed at the slowest speed, the movement of the object is still relatively clear and smooth. Therefore, the high-speed camera will occupy 3 channels of LSM-XT 150/3=50Hz, which meets the audience's appreciation requirements for slow-motion images, and at the same time, there will be no jumping of moving objects.
Applications of SportNet Network
The EVS SportNet network has shown strong macro-control in practical applications. Let's take a volleyball match as an example. Assume that camera No. 1 is a landline camera with a 50x lens, serving as the main broadcasting position; camera No. 2 uses a 20x lens, serving as an auxiliary camera position, and also serves as the A channel of the LMS-XT1 hard disk slow motion camera; cameras No. 3 and No. 4 use a 33x lens to shoot the serve shots of the athletes on both sides, and also capture the athletes' expressions and movements, serving as the B and C channels of the LMS-XT1; camera No. 6 is a 20x LDK-23 high-speed camera, providing high-speed LMS-XT2 hard disk slow motion; camera No. 7 is used for top shooting, serving as the D channel input of the LMS-XT1; the wide-angle lens of camera No. 8 is located in the center of the sideline, providing shots of net scrambles and serve errors, serving as the D channel input of the LMS-XT2; cameras No. 9 and No. 10 located at the two baselines serve together as the hard disk slow motion camera position of MAXS; camera No. 5 is used as a floating position to mainly shoot the coaches of both sides, and can be connected to the A channel of the LMS-XT3; camera No. 10 provides a side panoramic lens. Slow motion input signals can be selected through the matrix selection panel, which improves the flexibility of slow motion and relatively expands the number of slow motion camera positions. LMS-XT3 is mainly responsible for slow motion highlight production; if conditions permit, an Airbox can be added, which is connected to LSM XT and MAXS through the SDTI network. As the central editing index server of the OB vehicle, it manages all the materials in the network through the Windows database system, and can define, classify and sort keywords. Through Airbox, it is easy to prepare highlight packages, which can use materials from any EVS device in the network; loop broadcast, define different entry points and video transitions to make the highlights more exciting; even if it is broadcast online, the playlist can still be edited. From the storage of volleyball live broadcast materials to the complete packaging and broadcasting, including the production of fixed trailers, everything is available, as shown in Figure 3.
Figure 3 EVS SportNet network used for live broadcast of volleyball matches
With such a complete slow motion system, we can capture every wonderful shot on the field, and the division of labor is clear, only two slow motion production staff and one highlight production staff are needed. The MAXS of this system is only used as the MAP mirror channel of LMS-XT2, adding two camera channels; in fact, MAXS can also be used as a material storage or key generator, but it does not have the function of making highlights. Usually when we play back slow motion, there will always be a transition animation, which can be realized through MAXS. (End of full text)
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