10bit 03-422 10 bit pristine video quality
TRANSCRIPT
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Keeping Video Quality Pristin
throughout the Production Proc
4:2:2 10-bit AVC/H.264 encodPierre Larbier
ATEME (Burbank, USA & Bievres, France
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Agenda
Current States
Talk about the AVC/H.264 4:2:2 10-bit profile Empirical comparisons against 4:2:0 8-bit &
4:2:2 8-bit
Multi-Generation Encoding
Production Cases
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Production & Transmission Proce
Production uses 4:2:2 10-bit over SDI
Used in video editing, tape decks, file storage, etc
Video needs to be transmitted by internal system or a
networks
Todays transmission mostly uses
4:2:0 8-bit (MPEG-2 or AVC/H.264) for consumer app
4:2:2 8-bit(MPEG-2) for contribution applications
20-60 Mbps with latency from 1 sec-250ms
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AVC/H.264 Studio Profile VS. CuImplementations
Most AVC/H.264 products are currently geare
towards consumer video market 4:2:0 8-bit and
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About 4:2:0 Compression
Professional video sources are 4:2:2
4:2:0 compression requires resampling filters
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Progressive and Interlace chroma location schemes are d Challenges for existing chroma resampling architecture:
o Possible mismatch between the 2 resampling filters
o Resampling filters quality not guaranteed
o Choosing between Progressive and Interlace filters is not obvious
4:2:2 4:2:2 4:2:0
Downscaling
4:2:0
Encoding
4:2:0 4:2:2
Upscaling
4:2:0
DecodingSDI
Encoder Decoder
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4:2:0 Chroma Artifacts Mainly caused by a mismatch between downscale/upscale filte
o Color bleeding
o Chroma detail loss
o Interlace/Progressive artifacts
Worsen with each generation
Difficult to control in a Production chain
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After 5 4:2:2 4:2:0 conversions Source picture
Detail Loss
Color
Smearing Interlace
artifacts
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About 4:2:2 Compression At the 1st generation, with perfect resampling filters, 4:2:2 and
overall quality is roughly the same:
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But in multi-generation and/or with mismatched sampling4:2:2 quality is much better than 4:2:0
CrowdRun, 1080i25
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20 40 60 80 100 120 140 160 180 200 220
Bitrate (Mbps)
CombinedPSNR(dB)
4:2:0
4:2:2
4:2:2 vs 4:2:0 with perfect resampling filters
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Current 8-bit Compression Professional video sources are 10-bit
8-bit compression requires rounding before compression
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Motion compensation and loop-filtering performed using 8-b
Challenges for 8-bit architecture:
o Scalers match and quality not guaranteed
o Reduced accuracy in the encoding process reduces coding effici
o Luma shift caused by lack of rounding control
10-bit 10-bit 8-bit
Downscaling
8-bit
Encoding
8-bit 10-bit
Upscaling
8-bit
DecodingSDI
Encoder Decoder
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10-bit compression: banding rem Processing video with 8-bit sample depth may create banding
shallow changing light scenes:o Blue skies
o Underwater scenes
o Sunsets
These defects are not visible at 10-bit or more
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10-bit compression8-bit compression
Banding artifacts
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10-bit compression: increased coding e Coding efficiency is increased: less bit-rate for the same quality
Rate saving between 5% and 20% on most sources
Most of the gain is provided with 10-bit coding. With 12-bit andcoding efficiency gain is there but much smaller
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Woman with a Bird Cage, 1080i30
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0 15 30 45 60 75 90 105 120 135 150
Bitrate (Mbps)
PSNR
Y(dB)
8 bit
10 bit12 bit
Woman with a Bird Cage, 1080i30
0.00
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0 20 40 60 80 100 120 140 160 180
Bitrate (Mbps)
PSNRYgainr
elativeto8-bit(dB)
RD curve at 8,10 and 12-bit Distortion gain vs 8-bit comp
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10-bit compression: artifacts redu 10-bit compression reduces 3 kind of artifacts:
o Contouring
o Smearing
o Mosquito noise
As a side-effect, 10-bit compression also reduces random distor
shallow textured objects (clouds for instance)
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Contouring
Mosquito
Noise
8-bit compression 10-bit compressio
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AVC H422Pvs MPEG-2 422P H.264 H422P outperforms MPEG-2 422P in Contribution applic
o 10-bit support
o More than 20Mbps saved at Contribution rates!
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CrowdRun, 1080i25
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0 20 40 60 80 100 120 140
Bitrate (Mbps)
CombinedPSNR(dB)
Woman with a Bird Cage, 1080i30
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4142
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0 20 40 60 80 100 120 140 160
Bitrate (Mbps)
CombinedPSNR(dB)
MPEG-2
AVC/H.264
Example 2Example 1
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GOP Structure Types for Contrib GOP structure needs to be carefully considered
Possible Contribution GOP Structures
Intra-only, AVC-I, Short GOP, Adaptive Long GOP
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0 20 40 60 80 100 120
Average
PSNR
Y
Bitrate (Mbps)
Into Tree, 1080i25
Importance of GOP strucefficiency
Adaptive Long GOP and Short GOP give
better performance at same bit rate
Guide: let encoder make picture type
decision wherever possible
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Role of GOP in Multi-Generation En 3-4 Re-encodes can happen in a production transmission workflo
Aligning Encodes at GOP Boundaries can retain quality
PSNR Drop 3dB (Aligned) Vs 5dB (non-aligned) @ 7th
GEN
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1 2 3 4 5 6 7
A
veragePSNR
Y(dB)
Generation
ParkJoy 1080i25 @ 60Mbps - Aligned GOP
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IbBbI
Long GOP
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1 2 3 4 5 6
A
veragePSNR
Y(dB)
Generation
ParkJoy 1080i25 @ 60Mbps - Unalig
Multiple generations with aligned GOPS Multiple generations without a
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Production Uses Remote Truck Uplinks
Transmit in AVC 422 10-bit and at lower bit rates than MPEG-2 422P
Playout to Tape Infrastructures
Easily integrate transmission back into an SDI infrastructure (internationa
Remote Collaboration
Realtime 422 10-bit at lower bit rates
Multiple Generations Re-encodes
Typical Streams can re-encode 3-4 times before it gets to consumer, so tr
422 10-bit aligned GOP will preserve quality
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d
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Advantages Significantly lower transmission costs
Improve video quality on existing transmission links
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SummaryUsing 4:2:2 10-bit allows:
Process original source video in as close to an original form
Enables most demanding application in terms of quality & rate
Offers significant gain in quality and/or rate over existing solut
Reduces banding, smearing, and mosquito noise
Retains quality in production processes
Integrates into an SDI infrastructure at highest allowable qualit
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Thank-You
mailto:[email protected]:[email protected]