Post on 22-Dec-2015
G. Valenzise*, M. Tagliasacchi*, S. Tubaro*, L. Piccarreta
Picture Coding Symposium 2007November 7-9, 2007 – Lisboa, Portugal
*Dipartimento di Elettronica e Informazione,Politecnico di Milano
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Transmit multiple video streams over a shared channel◦ Broadcast television◦ Video-surveillance◦ etc…
The channel bandwidth is limited Equal bandwidth partitioning is not
optimal
band
wid
th
time
Stream 1
Stream 2
Stream 3band
wid
th
time
Stream 1
Stream 2
Stream 3
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Find an optimal way to allocate channel bandwidth among sequences
Example: two video sequences
time
time time
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Formulate the MINAVE and MINVAR problems in the -domain
Assumptions:◦ Constant bit rate (CBR) channel◦ Frame-by-frame optimization
Find a closed form solution for the MINVAR Compare the MINAVE and MINVAR criteria
◦ Check the coding efficiency loss for the average distortion
Relax the CBR assumption◦ Temporal smoothing
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Rate-distortion operational curve of each frame can be described in the ρ-domain (He and Mitra, 2002):
ρ-domain parameters can be estimated from decoded sequences
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
(He and Mitra, 2002)
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Which is equivalent to solving
When
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
MINAVE
MINVAR
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Average distortion of MINAVE
Average distortion of MINVAR
We know (by definition!) QUESTION:
◦ What is the coding efficiency loss?
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Average distortion of MINAVE
Average distortion of MINVAR
The coding efficiency loss is
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Relax the CBR assumption◦ Introduce a shared encoder buffer to perform VBR encoding
We apply the MINVAR rate allocation while at the same time achieving temporal smoothing
For each time instant:1.Compute the CBR distortion profile2.Smooth it with the low-pass filter (He, Zen and Chen, 2005)
3.Set Dsmooth as the target distortion and compute rates Ri
Relax or tighten the rate constraint according to the current buffer level
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
H.264decoder
H.264decoder
H.264decoder
...
H.264 bitstream
H.264 bitstream
H.264 bitstream
Rate controller
H.264encoder
H.264encoder
H.264encoder
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
MINAVE
MINVARsmoothed MINVAR
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
MINAVE
MINVARsmoothedMINVAR
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Summary:◦ Proposed a MINVAR bit allocation for multiplexed
video sequences◦ The MINVAR allocation leverages on the -domain
model (but works on any exponential model, i.e. at high rates)
◦ The coding efficiency loss w.r.t. MINAVE is, on average, of 0.5 dB
Future work:◦ Apply the MINVAR approach to Scalable Video
Coding solve a discrete optimization problem…
A -domain Rate Controller for Multiplexed Video SequencesPCS 2007, November 7, 2007
Questions?