Compressed domain spatial adaptation for H.264 video

Abstract

In this paper, we present a metadata-based compressed-domain spatial adaptation scheme for H.264/AVC video. We have enhanced the H.264/AVC encoder with our proposed adaptation strategies in order to reduce video size by cropping individual frames in an intermediary node prior to transmitting that video to heterogeneous devices. In this regard, we exploit the sliced architecture of the video frames within the first version of the H.264/AVC specification and devise different slicing strategies.The compressed-domain bitstream modification is performed at the intermediary nodes, avoiding the need for any cascaded operations. Here, we briefly present our adaptation scheme as well as evaluation results showing the effectiveness of the slicing strategies on the bitrate reduction and processing time. A comparison of our approach with an existing cropping scheme is also presented.

Modeling and Evaluation of a Metadata-Based Adaptive P2P Video-Streaming System

“…This is done by parsing the adapted metadata and then discarding those parts from the original bitstream that are missing in the adapted/transformed metadata. As discussed in [24], for spatial adaptation, it is preferable to have a smaller number of slices for each frame. The reason is that if we increase the number of slices, then it will eventually increase the overhead due to the added number of slice-headers.…”

“…For temporal adaptation, we drop frames from the compressed bitstream using a frame skip pattern [1], and for spatial adaptation, we drop slices outside of the region of interest (ROI) [24]. To implement our approach, we used gBSDUnitType and introduced gBSDFrameUnitType and gBSDSliceUnitType to describe each frame and slices with each frame, as shown previously in Box I. gBSDFrameUnitType consists of frame number, frame start, frame type and length of each frame for temporal adaptation.…”

“…The XSLT processor then generates the adapted gBSD containing the effective region for the frame based on the original spatial size and the requested spatial dimension (retrieved from UED information). As described in [24], for spatial adaptation, if any part of the slice belongs to the computed effective region, then the slice information is included in the adapted gBSD.…”