Rate control for MPEG transcoders Limin Wang; Luthra, A.; Eifrig, B.
IEEE transactions on circuits and systems for video technology,
02/2001, Letnik:
11, Številka:
2
Journal Article
Recenzirano
In MPEG, the input pictures can be coded in three different types: I, P, and B. The three pictures require quite different numbers of bits because of different natures of their temporal processing. ...Hence, an intelligent bit-allocation strategy should assign a picture the number of bits according to the picture's type, as well as the picture organization. This implies a requirement of a prior knowledge of the picture types for a given bit budget. This requirement is not a problem for the encoder, as the encoder can decide the type for each input picture. In fact, the encoder can plan ahead the types of the pictures. A transcoder however has no such a prior knowledge about a picture's type before actually processing the picture. This creates a difficulty in bit allocation for the transcoder. This paper presents a novel rate control scheme for MPEG transcoder that requires no a prior knowledge of the picture types. Our study indicates that the picture target rates determined by the proposed rate control with and without a prior knowledge of the picture types are very close.
The overall objective of these studies was to investigate, by experimental studies and theoretical analysis, the optimum annealing conditions to obtain maximum structural relaxation in lyophilized ...glasses of pharmaceutical significance. The model formulations used in this work were aspartame: sucrose and aspartame: trehalose (1:10 w/w) freeze-dried glasses. In this article, structural relaxation in amorphous systems was described in terms of the change in the fictive temperature (Tf) and was measured using the enthalpy relaxation endotherm in a differential scanning calorimeter (DSC). The theoretical analysis was performed using the Tool-Narayanaswamy-Moynihan (TNM) model. The effect of different annealing conditions (temperature and time) on fictive temperature obtained from the theoretical analysis was calculated and compared with the experimental results. The model reproduced the experimental data very well for samples that were quench cooled from the liquid. However, the model fits were poor for lyophilized samples, indicating an inability to incorporate the complex thermal history of freeze-drying in the TNM model. The optimum aging conditions were determined from both DSC and approximated best-fit parameters of the TNM model, and it was found that annealing when done at a temperature about 15–25°C below Tg resulted in maximum structural relaxation.
Introduction to the special issue on streaming video Civanlar, M.R.; Luthra, A.; Wenger, S. ...
IEEE transactions on circuits and systems for video technology,
03/2001, Letnik:
11, Številka:
3
Journal Article
COVID-19 caused by the SARS-CoV-2 virus has become a global pandemic. 3CL protease is a virally encoded protein that is essential across a broad spectrum of coronaviruses with no close human analogs. ...PF-00835231, a 3CL protease inhibitor, has exhibited potent in vitro antiviral activity against SARS-CoV-2 as a single agent. Here we report, the design and characterization of a phosphate prodrug PF-07304814 to enable the delivery and projected sustained systemic exposure in human of PF-00835231 to inhibit coronavirus family 3CL protease activity with selectivity over human host protease targets. Furthermore, we show that PF-00835231 has additive/synergistic activity in combination with remdesivir. We present the ADME, safety, in vitro, and in vivo antiviral activity data that supports the clinical evaluation of PF-07304814 as a potential COVID-19 treatment.
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