Video transcoding of scalable multi-layer videos to single layer video
View Patent ↗A method transcodes a compressed multi-layer video bitstream that includes a base layer bitstream and an enhancement layer bitstream. The base and enhancement layers are first partially decoded, and then the partially decoded signals are combined with a motion compensated signal yielding a combined signal. The combined signal is quantized into an output signal according to a quantization parameter, and the output signal is variable length encoded as a single layer bitstream. In a preprocessing step, the enhancement layer can be truncated according to rate control constraint, and the same constraints can also be used during the quantization.
1. A method for transcoding a compressed multi-layer video bitstream, comprising:
receiving, in a multi-layer to single-layer fine granular scalable transcoder, a compressed multi-layer video bitstream including a base layer and an enhancement layer;
partially decoding the base layer;
partially decoding the enhancement layer;
combining, in the DCT domain, the partially decoded base layer and the partially decoded enhancement layer with a motion compensated signal yielding a partially decoded combined signal;
quantizing the partially decoded combined signal into an output signal according to a quantization parameter;
inverse quantizing the output signal to yield a reconstructed partially decoded combined signal;
determining a difference between the partially decoded base layer and the reconstructed partially decoded combined signal;
generating the motion compensation signal using the difference; and
variable length encoding the output signal as a single layer bitstream.
2. The method of claim 1 wherein the quantization parameter is determined according to constraints and data extracted from the compressed multi-layer video bitstream.
3. The method of claim 2 wherein the constraints include rate control constraints.
4. The method of claim 3 wherein the rate control constraints are acquired from a network transporting the single layer bitstream.
5. The method of claim 2 wherein the constraints include buffer constraints.
6. The method of claim 5 wherein the buffer constraints are acquired from a device receiving the single layer bitstream.
7. The method of claim 2 wherein the constraints include complexity constraints including system processing load.
8. An apparatus for transcoding a compressed multi-layer video bitstream, comprising:
a multi-layer to single-layer fine granular scalable transcoder configured to receive a compressed multi-layer video bitstream including a base layer and an enhancement layer, the transcoder further comprising;
means for partially decoding the base layer;
means for partially decoding the enhancement layer;
means for combining, in the DCT domain, the partially decoded base layer and the partially decoded enhancement layer with a motion compensated signal yielding a partially decoded combined signal;
means for quantizing the partially decoded combined signal into an output signal according to a quantization parameter;
means for inverse quantizing the output signal to yield a reconstructed partially decoded combined signal;
means for determining a difference between the partially decoded base layer and the reconstructed partially decoded combined signal;
means for generating the motion compensation signal using the difference; and
means for variable length encoding the output signal as a single layer bitstream.