MM-4094, AMD Video Compression Engine: The Route towards Low-Latency Cloud Gaming Solutions, by Khaled Mammou and Ihab Amer

AMD VIDEO CODING ENGINE
THE ROUTE TOWARDS LOW-LATENCY CLOUD
GAMING SOLUTIONS

AGENDA

Introduction

AMD Video Coding Engine
Low Latency Encoding
Conclusions

2 | AMD VCE FOR LOW-LATENCY CLOUD GAMING | NOVEMBER 19, 2013

A LITTLE BIT OF HISTORY!
Perf/W

CPU

CPU

HW
IP

HWaccelerated
Video Coding

GPU

GPUaccelerated
Video Coding

CPU
CPU-based
Video Coding

2008/9

2011/12

Year

CPU VS. GPU VS. FIXED-FUNCTION-HW VIDEO COMPRESSION

CPU
 Pros
‒ No extra dollars
‒ Higher achievable qualities at target
bitrates (less architectural limitations)
‒ High Flexibility & Short Lead Time
‒ Can be optimized by advanced IS (e.g.
MMX)
 Cons
‒ Limited Operations per WATT
‒ Monopolized CPU
 Examples
‒ Handbrake/x264


 Pros
CPU+GPU
‒ No extra dollars
‒ Part of CPU available for other tasks
‒ SW-based – Still Flexible & relatively
Short Lead Time
 Cons
‒ Limited Operations per WATT
‒ Major design and code changes to
leverage parallelism
‒ Massive parallelism impacts
quality/bitrate
 Examples
‒ GPU-accelerated MainConcept Enc.
‒ GPU-accelerated x264

 Pros
Fixed-Function HW
‒ Fast!
‒ Power Efficient!
‒ Most of CPU available for other tasks

 Cons
‒ Additional Area Cost
‒ Least Flexible (hard coded)
‒ Long lead time
 Examples
‒ Applications in the market that
support:
‒ AMD VCE
‒ Intel Quick Sync
‒ NVIDIA NVEnc

AMD VIDEO CODING ENGINE (VCE)

VCE is AMD’s dedicated fixed-function
video coding engine for improved
video encoding performance


VCE TARGET PLATFORMS

AMD APUs

AMD Discrete GPUs

Server

Yes

Yes

Desktop

Yes

Yes

All-in-one

Yes

Yes

Premium Notebook

Yes

Yes

Value Notebook

Yes

Possible

Tablet

Yes

N/A


VCE MAIN USE CASES

(*) Courtesy of Cyberlink, Inc.

VCE

(**) Courtesy of CiiNow, Inc.

VCE CAPABILITIES
 Up to 3x 1080p@~30fps per instance

 Low-power budget

 Multi-streaming support

 Configurable speed/quality tradeoff

 Flexible/programmable to meet various use-cases


Bitrate

DESIGN ASPECTS OF VCE


VCE CREW – OUR EVERYDAY STORY!

“I don’t believe in perfection. I don’t think there is
such a thing. But the energy of wanting things to be
great is a perfectionist energy!”
Reese Witherspoon
Hollywood Actress & Academy Award Winner

“Have no fear of perfection – you’ll never reach it!”
Salvador Dalí
Spanish Painter/Artist


LATENCY IS KEY!
WHAT IS LATENCY?

 Latency is the elapsed time between the user’s input and his/her perception of the corresponding game reaction

−

< 100–150 ms
Game server
Game Engine

User
Display

Decoded
Picture
Buffer

Decoder

Code
Picture
Buffer

Network
Encoder
Buffer

Encoder

Rendering

Game client

Graphics Commands

Rendered Frame

Compressed Stream

Decoded Frame

NAL Units

Network Packets


LATENCY IS KEY!
WHAT IS ENCODING LATENCY?

 Encoding latency is the elapsed time between a frame is rendered on the server and it is decoded on the client

Game server
Game Engine

User
Display

Network

Decoded
Picture
Buffer

Decoder

Code
Picture
Buffer

Encoder
Buffer

Encoder

Rendering

Game client

Rendered Frame
Decoded Frame

Compressed Stream

NAL Units

Network Packets

ENCODE SPEED VS. QUALITY
HOW FAST CAN VCE ENCODE?

 VCE Quality Presets

1080p

720p

480p

Speed

95 fps

215 fps

535

Balanced

80 fps

180 fps

470

Quality

40 fps

90 fps

250


BUFFERING DELAY VS. QUALITY
WHY BUFFERING?

 Constant Quantization Parameter (CQP)
Instantaneous bitrate (mbits/s)

70

60
50
40
CQP

30

Avg. Bitrate (6Mbit/s)

20
10
0

0

10

20

30

40

50

60

Tranmission over a
Constant Bitrate (CBR)
channel of 6 Mbit/s ?

Frame number

Buffering
Transmission delay
(latency!)

BUFFERING DELAYS VS. QUALITY

Input Rate

WHAT IS CBR?

 Constant Bit Rate (CBR) Rate Control
Buffer

‒ Control transmission delays (i.e., # bits per picture) by adjusting QPs
‒ Leaky bucket model

Size (B)

‒ Defined by the triplet
‒ Avoid encoder buffer underflow and overflow (i.e., transmission bitrate = encoding bitrate)

Output Rate (R)

 Encoder can predict the decoder
buffer fullness

B

B

F

b2

b0 b1

b1

 Buffering latency is smaller than B/R

b2

b0
S0+De
S1

Fullness (F)

Decoder buffer
fullness

Encoder buffer
fullness

S0

Initial

S2

…

time

T0-Dd


T0

T1

T2

…

time

LATENCY VS. QUALITY
WHAT IS VBR?

 Variable Bit Rate (VBR) Rate Control
‒ Channel can stop transmission without loosing synchronization (e.g., packet based networks)
‒ Leaky bucket model
‒ Defined by the triplet
‒ Avoid only encoder buffer overflow (i.e., transmission bitrate may be higher than the encoding bitrate)

Allows shorter buffering delay

AMD Media SDK exposes two VBR modes:
Peak-Constrained VBR, and Latency-Constrained VBR

LATENCY VS. QUALITY
HOW BUFFERING LATENCY IMPACTS QUALITY?

 High buffering delay
‒
‒
‒
‒
‒

Peak-Constrained VBR
Target Bitrate = 6 Mbps
Peak Bitrate = 6 Mbps
VBVBufferSize = 6 Mbits (i.e., buffering latency of 1000 ms)
IDRPeriod = 60


70
60
50
40

VBR High Buffering Latency
30

CQP

20


10
0
0

10

20

30
Frame number


40

50

60

Reduce overshoots with
limited quality impact

LATENCY VS. QUALITY

 Low buffering delay
‒
‒
‒
‒
‒

Latency-Constrained VBR
VBVBufferSize = 0.1Mbits (i.e., buffering latency of 16 ms)
IDRPeriod = 60


70
60
50
40

VBR Low Buffering Latency

30

VBR High Buffering Latency
CQP

20

10
0
0

10

20

30
Frame number


40

50

60

Minimum buffering delays

LATENCY VS. QUALITY

 Low buffering delay
Frame 300 (IDR)

Poor IDR frames quality

Replace IDR frames with
partially intra-encoded frames


ERROR RESILIENCY VS. QUALITY
WHAT IS INTRA-REFRESH?

 Intra-refresh principle

IDR


P

P

P

WHAT IS INTRA-REFRESH?

 Intra-refresh principle
‒ Spread out Intra Units throughout successive pictures
‒ Constraint inter/intra-prediction to preserve error resiliency (i.e., Dirty/Clean Maps)

Restriction on
Search Region

I

D

D

D

C

Restriction on
Search Region


I

D

D

C

C

I

D

Restriction on
Search Region

C

C

C

I

HOW INTRA-REFRESH IMPACTS QUALITY?

 Intra-refresh with low buffering delay
‒
‒
‒
‒
‒

VBR Rate Control
IDRPeriod = 60



Frame 300 (IDR)



Frame 300 (Intra-Refreshed)

Improved IDR frames quality


COMPARATIVE EVALUATION
HOW GOOD IS VCE?

 VCE vs. Software Encoder
‒
‒
‒
‒
‒
‒

VBR Rate Control
IDRPeriod = 60
Intra-refresh


Software Encoder

COMPARATIVE EVALUATION
HOW GOOD IS VCE?

 VCE vs. Software Encoder
VCE


Software Encoder

CONCLUSIONS
 Fixed-Function HW acceleration is the prevalent technology for video compression
 AMD MediaSDK and RapidFire allow application developers to configure VCE parameters
‒ Latency/Error Resiliency/Quality
‒ Number of encoded streams/Power/NW-efficiency

 VCE offers an out-of-the-box solution for ultra-low latency cloud gaming
‒ Special rate control settings
‒ Intra-refresh support

 Deployed in the solutions of various cloud-gaming partners


DISCLAIMER & ATTRIBUTION

The information presented in this document is for informational purposes only and may contain technical inaccuracies, omissions and typographical errors.
The information contained herein is subject to change and may be rendered inaccurate for many reasons, including but not limited to product and roadmap
changes, component and motherboard version changes, new model and/or product releases, product differences between differing manufacturers, software
changes, BIOS flashes, firmware upgrades, or the like. AMD assumes no obligation to update or otherwise correct or revise this information. However, AMD
reserves the right to revise this information and to make changes from time to time to the content hereof without obligation of AMD to notify any person of
such revisions or changes.
AMD MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE CONTENTS HEREOF AND ASSUMES NO RESPONSIBILITY FOR ANY
INACCURACIES, ERRORS OR OMISSIONS THAT MAY APPEAR IN THIS INFORMATION.
AMD SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. IN NO EVENT WILL AMD BE
LIABLE TO ANY PERSON FOR ANY DIRECT, INDIRECT, SPECIAL OR OTHER CONSEQUENTIAL DAMAGES ARISING FROM THE USE OF ANY INFORMATION
CONTAINED HEREIN, EVEN IF AMD IS EXPRESSLY ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

ATTRIBUTION
© 2013 Advanced Micro Devices, Inc. All rights reserved. AMD, the AMD Arrow logo and combinations thereof are trademarks of Advanced Micro Devices,
Inc. in the United States and/or other jurisdictions. Other names are for informational purposes only and may be trademarks of their respective owners.


MM-4094, AMD Video Compression Engine: The Route towards Low-Latency Cloud Gaming Solutions, by Khaled Mammou and Ihab Amer

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MM-4094, AMD Video Compression Engine: The Route towards Low-Latency Cloud Gaming Solutions, by Khaled Mammou and Ihab Amer