Abstract: In a digital video tape recorder (DVTR), the video data are stored serially on a sequence of parallel scan tracks running obliquely across the tape. In normal playback, the read heads scan along each track sequentially, while fast-forward is realized by a special subsampling process in which the read heads sweep across multiple tracks per scan and pick up a segment of data from each track to generate a patchwork quilt of subimages taken from successive fields. An image compression algorithm for DVTR is required to conform to the storage format implied by this fast-forward mechanism. Thus, a field of video is partitioned into a small number of subimages, each independently coded with a fixed number of bits. This requirement excludes the use of interframe coding and most variable-rate coding algorithms. We propose a new image coding algorithm that retains the efficiency of variable-rate coding while the above requirement is satisfied. In this algorithm a subimage is partitioned into non-overlapping 8 $MUL 8 blocks, and each block is coded progressively by DCT and Vector Quantization to generate a finite set of candidate output blocks covering a range of bit rates. A procedure based on the Lagrange Multiplier method is used to select one of the candidate outputs for each 8 $MUL 8 block such that the overall distortion is minimized subject to the constraint on the bit rate. Simulation results demonstrate the potential of this algorithm in image compression for DVTRs.!
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机译：摘要：在数字磁带录像机（DVTR）中，视频数据被串行存储在倾斜穿过磁带的一系列并行扫描轨道上。在正常播放中，读磁头按顺序扫描每个磁道，而快速前进是通过特殊的子采样过程实现的，在该过程中，读磁头每次扫描扫过多个磁道，并从每个磁道中拾取一段数据以生成拼凑的被子从连续场获取的子图像集。要求DVTR的图像压缩算法要符合此快进机制所隐含的存储格式。因此，视频场被划分为少量的子图像，每个子图像都以固定数量的位独立编码。该要求不包括使用帧间编码和大多数可变速率编码算法。我们提出了一种新的图像编码算法，该算法在满足上述要求的同时仍保留了可变速率编码的效率。在该算法中，子图像被划分为不重叠的8个$ MUL 8个块，并且每个块都通过DCT和矢量量化进行渐进编码，以生成一组有限的候选输出块集，覆盖一定范围的比特率。使用基于拉格朗日乘数法的过程为每个8 $ MUL 8块选择候选输出之一，以使总失真在受到比特率约束的情况下最小化。仿真结果证明了该算法在DVTR图像压缩中的潜力。
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