In modern warfare, it is a key element to make video surveillance with mobile devices. However, the amount of the bandwidth to transfer the content is always limited. This causes the content to be highly compressed.
DAVKOM is both a video recording and a video transfer system.
It is designed to be used in mobile devices on wireless environments. On the mobile environment there are always limitations on the size, processor, power, and bandwidths. DAVKOM provides the most optimum solution for these type of environments. It adapts itself due to dynamically changing characteristics of a wireless environment, by, constantly monitoring network capacity and bit error rate, and altering coding parameters accordingly.
So even in harshest environments it continues video transmission.
DAVKOM consists of a transmitter and a receiver. Transmitter, transforms the anallog audio and video signal to digital, compresses the signal, and based on user selection it either transmits or stores the data. Receiver takes the signal, decodes the content, displays it and/or saves it for later references.
DAVKOM enables user to select over available frame rate and video resolution options in manual mode. In semi-automatic mode best frame rate or best video resolution options are available. In full-automatic mode system optimizes frame rate and video resolution together. User does not expected to intervene in this mode.
DAVKOM is designed as an embeded solution, however PC versions are also available.
Technical Specifications
- MPEG-4 AVC/H264: ISO/IEC 14496-10
- Platform: TI DM 642 DSP/PC
- Profile/Level: Extended baseline profile
- Input Video Format: YcbCr 4:2:2 and ITU-R BT.656 formated 8-bit resolution multiple digital video data
- Black and White / Colur video
- Coded video resolution: CIF, QCIF, SQCIF
- Coded video frame rate: 1 - 25
- Coded video bandwidths 4,8 - 64Kbps.
- Entropi Coding: CAVLC
- Motion detection estimation resolution: ½ pixels, ¼ pixels.
- Closed loop block differentiation filter
- Elastic Macroblock sequencing and desired cut sequence properties
- Automatic I frame placement
- Error Concealment
- Motion Balancing using noise filter
- Balancing of the contrast in input video
- Trace leaving defect canceling / removing
- High resolution encoding of a selected rectangle region defined with its 2 points
¼ Sub-pixel resolution Motion Estimation
During the motion detection, a block is searched in the previous frame for a closest match. It is possible to have ½ or ¼ sub-pixel detection rates instead of integer rates. By this way, it is possible to have much more similar blocks. Estimating the blocks in a much better way, improves the performance of the coding.
Automatic I-Frame Placement
I-frame, is a frame that can be decoded by itself. Automatic I-frame placement, detects a changing scene and places an I-frame in the video sequence. Therefore, it reduces the bit rate and processing requirement due to excessive amount of difference predictions.
Error Camouflage
If a code delivered to the decoder is faulty, erroneous regions occur in the decoded frame and the proceeding ones. In order to prevent this, some frames are coded in various pieces. For these pieces are encoded separately, non-erroneous regions can be decoded correctly. Furthermore, decoder camouflages the erroneous region by using interpolating the correct regions. This technique can provide uninterrupted video sequence for rather high bit rate channels.
Motion Balancing Noise Filter
While video acquisition, motion may cause some noises and artifacts, unwanted spots and pieces may occur. These types of noise increase the amount of high frequency components in a video. Therefore, they cause the coding performance to degrade. They are also disturbing to the user while watching the video. By reducing these type of noises the plausibiliy of the video is improved while coding efficiency is improved.
Brightness Compensation in the Input Video
Due to brightness changes in the scene, consecutive frames taken from exactly the same scene can result in high frame differences which will increase bit-rate of the coded data. Brightness changes are detected and brightness compensation is applied for better codec perormance.
Better Encoding of a Selected Region
This property of DAVKOM provides increased informatiion without increasing the overall bit rate. The main idea is to code selected region with better quality while slightly decreasing the coding quality everywhere else.
