MPEG2_benefits.pdf

MPEG2 benefits

People usually think that it is essential to use the same hardware for editing and

playout. This way of thinking is quite conservative and based on some widespread

myths about homogenous format usage, dated back in the days of tape-based editing

and playout. It is a well-proven rule, that sticking with a single tape format or single

video compression, best preserves the image quality throughout the whole post-

production process. Yes, this is true! It is the best choice when setting up a post-

production facility, to have in all of the workstations there the same type of hardware

platform, ensuring cross-compatibility and convenient group working. However,

when talking about playout, it is a little bit different story.

Using the same hardware for editing and playout (for instance 2xDigiSuite LE) has 2

clear advantages:

- you can reedit the on-air content without recompressing back to M-JPEG;

- you are 100% sure about content compatibility between the post-production facility

and the on-air suite.

Then the disadvantages come:

Cost - The playout hardware is as expensive as the editing one, even if you don't

have to use in complete its realtime capabilities. So, you have to buy at least 2x

DigiSuite/LE or LX/DTV – 1 for post-production, 1 for playout.

Export time - There is no existing playout software based on Matrox hardware, that

would let you playout an EDL. They all use single compiled AVI+WAV files (Export

Movie from Premiere, etc.). So, in all cases (MPEG2-based and non-MPEG2-based

playout) you would need to compile the final project as a single AVI+WAV file. This

takes exactly the same time when compiling to either DV, M-JPEG, MPEG2 I-frame

or MPEG2 IBP without MAX option (3-4 times slower than real-time). Moreover,

compiling to DV & MPEG2 can be accelerated (to realtime) by the MAX option,

while compiling to M-JPEG can not be accelerated by the MAX option.

Recompression - When compiling to single file, a recompression takes place, thus

quality loses can not be avoided even by using the same video compression.

Especially with real-time compiling by MAX option.

High bandwidth - The files (DV, DV50, MPEG2 I-frame, M-JPEG) are huge and

require special bandwidth in order to be transferred over a network. Typically most

TV Stations use SAN for that. This greatly increases the networking costs. While

MPEG2 files can be played-back from a network drive 100% reliably, using the

cheapest 100Mbit Ethernet network.

Storage - Being large, the files require extra storage space and it takes 5-10 times

more space than MPEG2 IBP. Storage costs are respectively 5-10 times higher.

Content exchange troubles - The system is closed and each incoming program from

external production houses has to be recaptured. This results in loss of time and

quality.

AirBox’s approach is using universal MPEG2 decoder hardware for playout. Content

ingest can be done by any MPEG2 encoder or by Matrox editing hardware. This

approach has only one disadvantage:

- The playout MPEG2 content is not easily editable anymore.

However this is not a real problem, since it is a rare occasion to reedit the playout

content. When such editing is needed, usually the editing project has been backed up.

Moreover AirBox does offer some simple cuts-only non-destructive MPEG2 editing

facilities without recompression!

Advantages of MPEG2-based AirBox playout:

Cost - The playout hardware can be quite inexpensive. This is due to the fact it

doesn’t include any special editing realtime features and DVEs. It is a dedicated

MPEG2 decoder from a wide variety of choices. For example, the cheapest MPEG2

decoder supported by AirBox up to date, is Sigma Designs Xcard (costs $100

approx).

Export time - MPEG2 export with DigiSuite MAX is real-time, when opposed to M-

JPEG export (3-4 times slower than real-time).

Open & Universal System - MPEG2 content can be received and instantly used

from several sources (satellite, content producers, DVD, etc.) without video

recompression, preserving the original content quality.

Low bandwidth - MPEG2 IBP does not require high-bandwidth networks. There are

existing PlayBox customers, running 3 TV channels simultaneously from the same

video hard disk set, on a simple 100 Mb/s Ethernet, even not 1 Gb/s. This means low

network traffic and costs.

Storage - For instance MPEG2 at 8 Mbit/sec takes exactly 1 MB/sec, when opposed

to 5-10 MB/sec for M-JPEG or 6.5 MB/sec for 50Mbit MPEG2 I-frame. This means

less hard drive space.

Effective compression –When we compare side-by-side an 8-Mbit/sec MPEG2 IBP

content and a 50-Mbit DV (or MPEG2 I-frame) content, we see no visible quality

difference. The key factor in IBP compression effectiveness, is the temporal

compression – P- and B-frames describe only the temporal difference with other

frames. That way the visual quality is preserved, while lots of redundant information

from the visual sequence is removed.

Flexibility - AirBox can equally well run MPEG2 IBP and MPEG2 I-frame up to 50

Mbits/sec. If the broadcaster is satisfied with low bitrate for long films and music

videos, he may require higher quality (or further editability) for the commercials. No

problem at all - in the same playlist AirBox plays both of the MPEG2 profiles. There

is a wide variety of low-cost or high-end MPEG2 encoders available. Your choice is

not restricted to a single hardware manufacturer.

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