Variable Frame Rate Research Articles

Three-Dimensional Transesophageal Echocardiography Is a Major Advance for Intraoperative Clinical Management of Patients Undergoing Cardiac Surgery

Echocardiography is a key assessment tool for the evaluation of cardiac structure and function. The ability to image cardiac structures using 3-dimensional (3D) echocardiography is evolving. In this article, we present some of the key features of the emerging 3D technology and review its applications with an emphasis on real-time 3D transesophageal echocardiography.

Variable frame rate control jerkiness-driven

We are introducing a real-time variable frame rate control scheme capable of optimizing both spatial and temporal video qualities. It traces the motion of incoming video frames and automatically tunes the outgoing frame rate according to the level of jerkiness acceptable by the user. The control scheme was conceived within the framework of mobile communications, which require an optimum use of both the available bandwidth and terminal resources. We have designed and implemented a video transcoding architecture which supports our frame rate control. The transcoder has been developed at the Coritel laboratories, Rome, Italy (Coritel is a research consortium managed by Ericsson Lab, Italy, and the University of Rome La Sapienza), while the visual tests were carried out at the ISCOM laboratory, Italian Communication Ministry, Rome, Italy. The proposed transcoding architecture is compatible with the constraints of real-time communications and it has been extensively tested under a wide range of conditions. We then present a subjective assessment of our solution carried out in a fully equipped professional laboratory. Within this assessment a number of non-expert viewers were asked to express their preference when watching side by side the same video, coded at a variable frame rate and at a fixed frame rate. Results show that in most cases a variable frame rate control based on a dynamic bit/frame allocation scheme might substantially improve video quality perceived by viewers.

An efficient frame selection approach to variable frame rate analysis for noise robust speech recognition

This paper presents a low-complexity, effective variable frame rate (VFR) analysis method that conducts frame selection on the basis of a posteriori signal-to-noise ratio (SNR) weighted energy distance. It has two characteristics. First, energy distance (instead of cepstral distance) is used to make it computationally efficient and thus enable a finer granularity in search as compared with cepstral distance criterion. Secondly, SNR weighting is used to emphasize the reliable regions in noisy speech signals. In terms of frame selection, it is experimentally found that the method is able to assign a higher frame rate to fast changing events such as consonants, a lower frame rate to steady regions like vowels and no frames to silence, even for very low SNR signals. The VFR method is applied to speech recognition in noisy environments to improve noise robustness. Being a method that takes effect in the time-domain, it is moreover combined with spectral- and cepstral-domain techniques to gain further improvement. Experiments are conducted on the Aurora 2 database, which is the TI digits database artificially distorted by adding different noises, and very encouraging results are obtained.

The impact of varying frame rates and bit rates on perceived quality of low/high motion sequences with smooth/complex texture

There are evidences to indicate that a user's perception is affected by varying frame rate and bit rate with respect to different video content characteristics. We attempt to understand the differences of motion and texture characteristics by adopting both the objective assessment and the subjective assessment methodologies. In this paper, the peak signal-to-noise ratio (PSNR) is used as the objective measurement, while the double stimulus continuous quality scale (DSCQS) is used as the subjective measurement. We find that the low motion characteristic sequences suit to low frame rates while the high motion characteristic sequences suit to high frame rates under the limited bandwidths. The perceived quality of the complex texture characteristic sequences has significant difference at different bit rates. The results indicate that a multimedia scheduling system for transmitting the low motion and smooth texture (Type 1) sequences and the low motion and complex texture (Type 2) sequences should reduce frame rate to increase the bits of frame under the insufficient bandwidth, whereas the high motion and smooth texture (Type 3) sequences and the high motion and complex texture (Type 4) sequences should keep frame rate to decrease the bits of frame. The perceived quality of Type 1 and Type 3 sequences can be improved by increasing bit rate more than Type 2 and Type 4 under the limited bandwidth.

Fluoroscopy: basic science, optimal use, and patient/operator protection

Fluoroscopy is an x-ray-based medical imaging technique that is used when viewing a real-time process within the human body is important. Examples of use for fluoroscopy include swallowing studies, upper and lower gastrointestinal imaging, angiography, as well as device placements such as stents, needles, lines, and tubes. Because of its widespread applications, fluoroscopy is found in many areas of modern hospitals. Areas often using fluoroscopy include radiology, gastroenterology, surgery, pain management, cardiology, and others. Today, most modern units deliver x-rays as short pulses instead of continuously, thus lowering the radiation exposure to patients and operators. The source for x-rays in a modern fluoroscope is an x-ray tube. An x-ray tube is a device that permits the energy and number of x-rays produced to be controlled independently. Image receptors in fluoroscopy have recently undergone a revolutionary transformation from largely analog devices to mostly digital devices. Continuous mode fluoroscopy is a mode found on many older models and continues to be provided on some newer models. Variable frame rate fluoroscopy has been of substantial benefit to patents and operators. In this mode, an operator selects the frame rate or frames per second at which images will be collected. Radiation dose in fluoroscopy is directly proportional to the amount of time the x-ray beam is on. Distance is the single most important parameter that can be modified to minimize fluoroscopic operator dose. In adults, it would be advisable to keep the kVp in the range from 80 to 110 kVp for most routine applications to keep patient and operator doses reasonable. Overuse of magnification modes is also a major contributor to high patient and operator doses. Personnel protective apparel when using fluoroscopy as part of your practice is critical to staying safe.

Dynamic frame-skipping transcoding with motion information considered

Frame-skipping transcoding is an efficient tool for reducing the bit rate when transmitting precoded video over bandwidth-constrained channels. In this process, the motion information is an important factor to be considered. Traditional methods consider only the motion activity information in dynamic frame-skipping transcoding. The concept of motion change is introduced to evaluate motion continuity. Combined with the motion activity information, these two parts of motion information are used to dynamically skip frames without seriously affecting the visual quality. A new frame-skipping scheme with a variable length prediction window is also proposed. Experimental results show that the proposed method can present a smooth frame rate variation, and well preserve the original motion information with tolerable delay. At the same time, spatial quality is also improved.

Pulse frequency modulation based CMOS image sensor for subretinal stimulation

We have developed a CMOS image sensor based on pulse frequency modulation for subretinal implantation. The sensor chip forms part of the proposed intraocular retinal prosthesis system where data and power transmission are provided wirelessly from an extraocular unit. Image sensing and electrical stimulus are integrated onto the same chip. Image of sufficient resolution has been demonstrated using 16/spl times/16 pixels. Biphasic current stimulus pulses at above threshold levels of the human retina (500 /spl mu/A) at varying frame rates (4 Hz to 8 kHz) have been achieved. The implant chip was fabricated using standard CMOS technology.

Optimal Temporal Sampling Aperture for HDTV Varispeed Acquisition

According to the perceptions of the human visual system, optimization of the temporal sampling aperture is required to best convey motion blur during HDTV image capturing. Filtering temporal aliasing artifacts becomes possible with the latest technologies in picture acquisition, and is applicable for advanced tape-based or tapeless recording. This paper presents an analysis of video capturing and recording in HDTV, for the case of variable frame rate (varispeed) acquisition. It proposes an optimization of the exposure duration, so that the duration becomes dependent on the frame rate of the master format. This approach restrains the strobe effect and utilizes motion blur for better rendering of dynamic scenes. The improved overall image quality also benefits the processes of editing, compositing, conversion, and compression. Finally, the research results are integrated into an embedded algorithm to suggest how to implement this strategy.

Development of Variable Frame Rate Camera recorder “Varicam” for Digital Cinema

Development of Variable Frame Rate Camera recorder “Varicam” for Digital Cinema

Optically imaging cardiac activation with a laser system.

The authors have developed a laser imaging system that: 1) depicts potential distribution with high spatial and temporal resolution; 2) can image large areas; 3) does not require filtering for signal or image enhancement; 4) is flexible, allowing for the acquisition of images of programmable size and shape at varying frame rates; and 5) has a large depth of field, thus minimizing the loss of focus when simultaneously imaging areas of the heart at different distances from the prime focal plane. The high duality of the images obtained with this technique allows quantitative measurements to be made of both the potential distribution and the change in this distribution over time. Here, the authors discuss the components of the system and the present their experimental results.

Modeling and control of VBR H.261 video transmission over frame relay networks

Examines the transmission of variable bit-rate (VBR) H.261 video over a mixed traffic (video/inter-LAN) integrated services frame relay (FR) network. We introduce a modified H.261 codec that produces VBR output and show that parsing of the video bit stream at group of blocks (GOB) boundaries produces variable length FR packets well suited to the network. We demonstrate that GOB-level video traffic requires a more sophisticated statistical model of the resulting data stream than the frame-level models. The transform expand sample (TES) method is used to obtain an accurate model of the autocorrelation and the marginal probability distribution of the bit-rate variations at the GOB level. A simple and effective methodology is introduced for capturing the periodic components that are present in the GOB-level autocorrelation. The methodology is extended to permit simulations of VBR codecs in which the codec quantization step size is adjusted in response to prevailing network conditions. We show that the quality of service requirements of VBR video can be met by using the FR backward explicit congestion notification (BECN) facility in conjunction with a modified H.261 codec whose rate is controlled by the congestion notification. We also show that the performance of the control mechanism is significantly influenced by a subset of network threshold and codec control parameters which are identified using 2/sup k/ factorial analysis techniques. We obtain optimal ranges of values for these parameters using mean field annealing. Variable quantization rate control may be more effective for this purpose than variable frame rate control.

Source model for transform video coder and its application. II. Variable frame rate coding

In the first part of this paper, we derived a source model describing the relationship between bits, distortion, and quantization step size for transform coders. Based on this source model, a variable frame rate coding algorithm is developed. The basic idea is to select a proper picture frame rate to ensure a minimum picture quality for every frame. Because our source model can predict approximately the number of coded bits when a certain quantization step size is used, we could predict the quality and bits of coded images without going through the entire real-coding process. Therefore, we could skip the right number of picture frames to accomplish the goal of constant image quality. Our proposed variable frame rate coding schemes are simple but quite effective as demonstrated by simulation results. The results of using another variable frame rate scheme, Test Model for H.263 (TMN-5), and the results of using a fixed frame rate coding scheme, Reference Model 8 for H.261 (RM8), are also provided for comparison.

994-95 Variability Sources in Quantitative Coronary Arteriography

In a trial of progression/regression of coronary artery disease the results of quantitative coronary arteriography are affected by the following main factors: (i) the frame selected for analysis (FRAME), according to the general agreement, that the lesion should be measured at enddiastole. (ii) the frame rate (RATE), To obtain a truely enddiastolic image of a coronary lesion, a cine frame rate of 25 frames/sec is mandatory up to date. Newer digital equipped systems allow to use a frame rate of 12.5/sec, but there is concern, that one miss a truely representative enddiastolic image. (iii) the measurement variance (MEAS) obtained from repeated measurements. We analyzed the impact of these variability sources on the measurements in a study of 29 coronary lesions. The lesions were filmed at 25 and 12.5 frames/sec. The truely enddiastolic frame as well as the frame preceeding and following it was analyzed. Each frame was measured twice, using computer-assisted analysis of vessels. A nested multivariate analysis of variance was developed to quantify the effects of the independent variables RATE (12.5 instead of 25/sec), FRAME (enddiastole or a frame deviating from it) and MEAS (measuring the same frame twice) on the “outcome” in the sample the mean % diameter stenosis. The total variance in the sample by considering different stenosis (STEN; 15–75% diameter stenosis) was set to 100%. Multivariate analysis of variance shows the following influence of the various components on the size of % diameter stenosis: Independent variable STEN FRAME RATE MEAS Coefficient of variation 23.67 9.23 4.38 5.70 % contribution to total variance 100 15.20 3.40 5.90 Frame selection is the major source of variability quantifying coronary lesions. Compared to the total variance the variance attributable to frame selection is nearly 3 times higher than the measurement variance and nearly 5 times higher than the rate attributable variance. Thus, one hasto take great care of selecting appropriate frames and may use the lower frame rate (12.5/sec) to reduce radiation exposure and facilitate digital image archiving.

A new variable frame analysis method for speech recognition

Variable frame rate (VFR) analysis is a technique used in speech processing and recognition for discarding frames that are too much alike. The article introduces a new method for VFR. Instead of calculating the distance between frames, the norm of the derivative parameters is used in deciding to retain or to discard a frame, informal inspection of speech spectrograms shows that this new method puts more emphasis on the transient regions of the speech signal. Experimental results with a hidden Markov model (HMM) based system show that the new method outperforms the classical method. >

A New High-Speed Spectral Infrared Imaging Device Applied for Flame Studies

Abstract A high-speed spectral infrared imaging system has been developed for facilitating investigation of thermal processes, including those in combustion devices. The new system has several unique performance characteristics: variable and high speed frame rate; variable and short exposure period; independent control of imaging parameters; digital imaging in high dynamic resolution; spectral imaging, externally triggered individual images, and large number of frames per each data acquisition. Its design and performance verification was made by obtaining instantaneous thermal images that permit visualization of reaction fronts and subsequent mixing of combustion products of a Bunsen burner, a rectangular Poiseuille-flow burner, and a spark-ignition engine. Some results from this work are compared with those obtained using conventional methods reported in other literature. It is demonstrated that findings, otherwise difficult to obtain, are made possible by this newly developed tool.

Variable frame rate analysis in the ARM continuous speech recognition system

The application of a simple variable frame rate analysis to the RSRE Airborne Reconnaissance Mission System, a continuous speech recognition system based on phone-level hidden Markov models, is described. Results are presented which show that performance using the variable frame rate technique and triphone models can be better than that obtained using triphone models and full frame rate data. The variable frame rate technique requires considerably less processing time.

Variable frame rate, fixed bit rate vocoding method

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The use of variable frame rate analysis in speech recognition

The application of a simple variable frame rate analysis to a continuous speech recognition system based on phone-level hidden Markov models, is described. Results are presented which show that, using standard three-state models, the addition of the variable frame rate analysis results in considerably improved performance, which is close to that obtained using simple duration sensitive models.

Speech synthesis integrated circuit device having variable frame rate capability

An integrated circuit device or chip digitally synthesizes human speech employing a linear predictive filter and a variable frame rate. The variable frame rate provides a more natural speech by slowing or speeding the frame rate for a particular application used in a system which constructs the speech data to be synthesized from allophone codes. The speech synthesis system incorporates a controller, such as a microprocessor, therein. The controller furnishes to the speech synthesizer a control signal (CTL 1, CTL 2) via an input (73), the control signal being used within the speech synthesizer to alter the timing signals, thereby altering the frame rate. The control signals are in binary code and are decoded by a decode and counter preset circuit (72). The decoded outputs load a counter (71) to the determined value, and the outputs of the counter and a programmable logic array are then decoded by a timing output decoder (74) to produce one of a plurality of possible signals indicating the frame speed for the frame just loaded.

Speech synthesis system utilizing variable frame rate

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