Production Technology Seminar 2009 - EBU Technical

The EBU Recommendation R 124 12 , accessible to all publics, provides guidelines for the 'Choice of
HDTV Compression Algorithm and Bit rate for Acquisition, Production and Distribution'.
1.6 HDTV Distribution Encoder Tests Results
Rainer Schaefer, Head of Production Systems TV, IRT, Germany
The previous report of the P/HDC group work [4] was presented in January 2008 13 .
For the tests, two sets of sequences were assembled from transparent sources and from the former
P/HDTP group [6]-[7]+[20]. The parameters used for evaluation were:
� Formats: 1920 x 1080i/25, 1440 x 1080i/25, 1280 x 720p/50
� Bit-rates: 6 to 20 Mbit/s in steps of 2 Mbit/s
� GOP structures (with an I-frame distance ~ 0,64 s): N16M3 for 1080i/25, N32M3 for 720p/50, and
dynamic GOP enabled, if supported.
The H.264 (MPEG-4 AVC) encoders used for evaluations, during two experts viewing sessions, were:
Ateme Kyrion (status Q3/07), Harmonic Electra 7000 (status Q3/07), Scientific Atlanta D9054 (status
Q3/07), Tandberg EN8090 (status Q3/07, and status Q2/08 optimised), GVG/Thomson Vibes EM3000
(status end Q4/08). The state-of-the-art HD MPEG-2 encoder Sciatl D9050 was used as an anchor and
reference. Three different tests were undertaken, with the following results:
Test Tasks Test results
Step 1
Distribution only
[12]+[17]
Step 2
Distribution only
[13]+[18]
Cascaded
4th generation
Production
+ Distribution
[14] + [20]
Identify critical sequences
of the whole set of
sequences and record
general observations on
H.264 encoder
Find the bit-rate of device
under test to match an
"upper anchor“ (24 Mbit/s
of the reference MPEG-2
encoder).
Identify whether
production encoder
stresses distribution
encoder at low bit-rates
and whether production
encoder limits distribution
quality at high bit-rates
12 http://tech.ebu.ch/docs/r/r124.pdf
13 Cf. Production Technology seminar 2008 report - § 2.5
H.264 (MPEG-4 AVC) codecs are generally better than an MPEG-2 encoder
operating at twice the bit-rate
Generally less coding artefacts for AVC except for grass and diva
On average MPEG-2 (at doubled bit-rate) & H.264 are comparable for
critical scenes; just perceptible loss of resolution for some scenes in H.264
depending on the codec optimisation
Visible artefacts for sequences.... (Diva, Oly Flags...) at low bit-rates such as
6..8 Mbit/s H.264
Sometimes perceptible loss of sharpness for H.264 (one encoder, certain
sequences...), depending on optimization of encoder
Good sharpness in general...
GOP pumping perceptible to very perceptible in some sequences (...)
GOP pumping in sub-areas of certain sequences
…
According to the formats, the following average bit-rates of the 5 codecs
tested were needed to match:
1920 x 1080i/25: 12,833 Mbit/s (8 - 16 Mbit/s interval)
1440 x 1080i/25: 12,133 Mbit/s (10 - 14 Mbit/s)
1280 x 720p/50: 10,533 Mbit/s (8 - 14 Mbit/s)
At high bit-rates:
No significant impairments of production encoder and type of production
encoder visible
In some cases: It may be the case that the picture quality has improved
for720p/50 in such a way that differences now become more visible
At low bit-rates:
Just perceptible loss of resolution at 3H vieving distance
Just perceptible increase of coding artefacts at 3H
GOP pumping in certain sub-areas of critical sequences
Perceptible increase of noise for certain sequences
In summary: no significant dependency on any production encoder!
© EBU 2009 / Production Technology seminar / January 27 - 29, 2009
Reproduction prohibited without written permission of EBU TECHNICAL & EBU TRAINING
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