Of itu-t sg16 wp3 and iso/iec jtc1/SC29/WG11

6.2SHVC (20)

6.2.1General (0)

6.2.2SCE1 related (arbitrary scalability ratio) (0)

6.2.3SCE2 related (key picture concept and single-loop decoding) (2)

(Reviewed Sat 26th afternoon JRO)

JCTVC-O0127 Transcoder-friendly scalable coding [Kenneth Andersson, Thomas Rusert, Rickard Sjöberg, Jonatan Samuelsson (Ericsson)]

To be able to provide scalability with high coding efficiency both from an encoding device to a network node (uplink) and from the network node to the end user device (downlink) this contribution proposes to add new functionality to SHVC. It is proposed that the transform coefficients of a low fidelity layer can be derived from transform and quantization of the difference between the reconstructed pixel values of the high fidelity base layer and the prediction from the low fidelity layer. This enables BDR gains compared to simulcast of 12.1% for SNR scalability at the same time as the high fidelity base layer can be represented without any loss compared to single layer HEVC and also be compatible with HEVC version 1 in the down link to the end user device. The BD rate of the dependent layer is reduced by 35.7% compared to having the layer independently coded. This contribution proposes to add an additional decoding process before the inverse quantization and inverse transformation for the dependent layers. The use of the proposed decoding process is indicated in the VPS.

It is suggested that this new functionality can be used by a transcoder to get a HEVC version 1 high-fidelity bitstream by only removing higher layer NAL units and that Transcoding of the scalable bitstream to a low fidelity HEVC version 1 bitstream can be done without computationally demanding mode decisions and motion estimation.

Requires low-level changes for the dependent (low fidelity) layer – would not fit with the current SHVC spec.

Gain versus simulcast is lower than in SHVC SNR scalability (RA 13% proposal / 20% SHVC; LD-B 11/12%)

In the network, the effort for low-fidelity bitstream generating is more complex than bitstream extraction of SHVC

Both low and high fidelities can be decoded by legacy devices (at the expense of network processing)

Application: Multicast

For the application, it would be interesting to compare to “bitstream rewriting” approach (which is not available in SHVC and would also require low-level changes for EL)

The approach could rather be called “guide transcoding with side information” than scalable coding and likely is less complex than traditional transcoding (but still more complex than bitstream extraction)

Performance comparison against light weight transcoding with comparable complexity (e.g. just re-quant. of coefficients) would be interesting.

Several experts expressed interest for the approach. It was also suggested that combination with spatial scalability would be interesting.

Further study (also an input to MPEG requirements).