Maria Pantoja

Coefficient Conversion for Transform Domain VC-1 TO H.264 Transcoding

This paper discusses the problem of transcoding between VC-1 and H.264 video standards. VC-1 uses an adaptive block size integer transform, which is different from the 4×4 integer transform used by H.264. We propose an algorithm to transcode the transform coefficients from VC-1 to those for H.264, which is a fundamental step for transform domain transcoding. The paper also presents a fast computation version of the algorithm. The implementation of the proposed algorithm shows that the quality of the video remains roughly the same while the complexity is greatly reduced when compared with the reference full cascade pixel domain transcoder.

A two-level rate control approach for video transcoding

We present a two-level rate control approach for VC-1 to H.264 transcoding. First, a low complexity algorithm in which the key is to find the relationship between quantization parameters (QPs) in VC-1 to QPs in H.264. Second, a medium complexity algorithm in which the key is to use mean absolute differences and sum of absolute transform differences calculated in VC-1 to estimate the complexity of macroblocks in H.264 for a pixel/transform domain transcoder. The low complexity rate control tool has a limitation of only able to rate-control transcode for QP ranges from 10 to 29. To transcode the entire QP range we propose a combination of low and median complexities tools. Results show that the proposed rate control transcoding is less complex than that of a full-cascaded transcoder with regular rate control turned on, while maintaining target bit-rate and PSNR.

Programmable Deblocking Filter Architecture for a VC-1 Video Decoder

Although the current standards (MPEG1, MPEG2, MPEG4, H.261, H.263, and H.264/MPEG4 AVC) as well as the recent VC-1, present the same basic functional elements, i.e., prediction, transformation, quantization, and entropy encoding, important changes occur in the details of each functional element. One of the details concerns the elimination of the loss in interblock correlation due to block-based prediction, transformation, and quantization. In order to overcome the loss in blocking artifacts, a deblocking filtering method is necessary to maximize coding performance and consequently improve image quality. This letter describes a programmable VC-1 deblocking filter architecture with capabilities to support different standards. The architecture has been modeled, simulated, and implemented at the register transfer level. Results show a threefold performance improvement as compared to solutions where filtering algorithms are otherwise not hardwired. Results also point to parallelism based on existing data flow, and show that real-time requirements can be met.

A multi-standard micro-programmable deblocking filter architecture and its application to VC-1 video decoder

In order to overcome the loss in blocking artifacts due to block-based prediction, transformation, and quantization, a de-blocking filtering method is necessary to maximize coding performance and consequently improve image quality. This paper describes a programmable VC-1 de-blocking filter architecture with capabilities to support different standards. The architecture has been modeled, simulated and implemented in RTL. Results show a threefold performance improvement as compared to solutions where filtering algorithms are otherwise not hardwired. Results also point to parallelism based on existing data flow and show that real-time requirements can be met.

P-Frame Transcoding in VC-1 to H.264 Transcoders

VC-1 is now one of the three video coding standards for high definition DVD that include MPEG-2 and H.264. The coded is expected to be used in consumer electronic devices such as DVD and camcorders. The H.264 format has begun to see strong acceptance and is used in mobile devices such as iPod and mobile phones. While multi-format DVD players are expected to support the three high definition video coding formats, H.264 is expected to have broader support in devices and video download services. The need to move data among devices with different capabilities creates a need for transcoding. In this paper we present a P-frame transcoder for VC-1 to H.264 transcoding. The transcoder exploits the variable size transform used in VC-1 to select the variable block size for motion compensation in H.264. The transcoder reduces the complexity substantially without significant loss in quality.

Low complexity rate control for VC-1 to H.264 transcoding

In this paper we focus on rate-control VC-1 to H.264 video transcoding in which video quality is obtained while maintaining a target bit rate for the transcoded output. The relationship between rate control in VC-1 and H.264 is studied and we use the rate control information obtained from VC-1 encoding to simplify the rate control algorithm in H.264. The key idea is to find the relationship between the quantization parameters (QPs) in VC-1 to the QPs in H.264 so that the first can be used to estimate the second, short cutting the need for a complex estimation in H.264. Experimental results show that the proposed rate control for transcoding is less complex than that for a full cascaded decoder while maintaining the target bit rate and PSNR.

Transcoding with Resolution Conversion Using Super-Resolution and Irregular Sampling

In transcoding, quantization and other techniques could result in lower video output quality. To address this problem a novel super-resolution (SR) algorithm based on irregular sampling (IS) is presented in this paper. The high-resolution (HR) frame is obtained as an interpolation of one or more previous frames; the resulting interpolated frame has samples non-uniformly spaced in the areas where movement happened. To reconstruct the irregular sampled frame we use a well-known irregular sampling algorithm modified to perform in 2-D space. Moreover, because SR algorithms are in general computationally expensive, we also present a hardware feasibility study. The proposed solution does not target any specific application but we have specifically tested the algorithm in a transcoding environment. In particular, we have applied it to VC-1 to H.264 transcoding and applied down/up sampling. Experimental results show that the proposed algorithm improves video quality significantly.

Adaptive transform size and frame-field selection for efficient VC-1 to H.264 high profile transcoding

In this paper, we present a novel technique to transcode VC-1 to H.264 high profile (HP). We use the low frequency AC coefficients to estimate the homogeneity of the block to predict the block transform size and use the magnitude of the motion vectors to help decide transcoding mode for interlaced video. We also analyze the drift error specific to transcoding VC-1 to H.264 and apply this study results to improve final video quality. Implementation of the solution shows that the complexity of the transcoder, when compared to a full-cascaded transcoder, is greatly reduced without a significant loss in peak-signal-to-noise ratio (PSNR).

Automatic Pronunciation Assistance on Video

In this article we present a novel method that uses image and speech processing techniques to analyze video from a second language learner and provides speakers pronunciation training. The pronunciation recommendation provided for the speaker will be selected from a database using machine learning techniques The model presented integrates speech and image recognition technology capable of quantizing and analyzing the learners input providing feed-back data to evaluate the models performance. The image/audio analysis and the expert system needed to provide recommendations to students are implemented on the GPU to allow for a fast feedback to students. Results show that our methodology accurately assigns pronunciation recommendations equivalent to those provided by a human second language (L2) instructor.

Transcoding with quality enhancement and irregular sampling

The need to move data among devices with different capabilities creates a need for transcoding. In this paper, an efficient transcoding algorithm from VC-1 to H.264 video with down/up sampling is discussed. Transcoding with resolution conversion usually results in lower video output quality. To address this problem an algorithm for quality enhancement with the use of irregular sampling is presented to use with transcoding. The quality enhancement module can also be used independently from the transcoding step. Experimental results show that the proposed algorithm can successfully remove artifacts and generate higher video quality. The main contribution of this paper is the use of irregular sampling techniques for video quality enhancement.