Mpeg For The Media Sonic Players

A Division of Electrosonic
MPEG for the MediaSonic Players

Orlando Moreno
omoreno@hotmail.com
408.656.2498

Only what you need to know!

Equation 1: Forward Discrete Cosine Transform

omoreno@hotmail.com 408.656.2498

MPEG only what you need to know!

• MPEG is a compression standard, currently we
use MPEG2 on the Players.
• An MPEG file contains Video and Audio in
discrete streams called ELEMENTARY streams.
Time stamps are used to synchronize the
streams.
• These streams are MULTIPLEXED together
either as a PROGRAM or TRANSPORT stream.
• This is all bad news!


Program / Transport

• Electrosonic SD Player uses MPEG2
Program Streams that are designed for
storage and playback from disk.
• MediaSonic DTV Players use MPEG2
Transport Streams designed for
transmission over communication systems
like ATM and broadcast. They are
designed to recover from error not perfect
playback!


MPEG Encoder

Audio Data Mpeg Encode Audio PES
Packet
Multiplexer Multiplexed
Stream

Video PES
Video Data Mpeg Encode
Packet

System Clock


Hardware MPEG Video Encoder

HDSDI
4.2.2 @ 10bit 4.2.0 @ 8bit DCT

D5 is 4.2.2 – 10 bit
HDCAM is 3.1.1 - 8 bit

Color Sampling Standards
P P P P
Line 1 PR B PR B PR B PR B
Y Y Y Y Y Y Y Y

P P P P
Line 2 PR B PR B PR B PR B
Y Y Y Y Y Y Y Y

4.2.2

Line 1
Y Y Y Y Y Y Y Y
P P P P
PR B PR B PR B PR B

Line 2 Y Y Y Y Y Y Y Y

4.2.0

Video Compression

P Frames

B Frames

I Frame

Group of Pictures in
Encoder Sequence


Headers

Sequence
Group of Pictures
Header

GOP
Header


Video - Things to remember.

• GOP is usually half a second long, so 15
frames for NTSC and 12 for PAL.
• A ‘Closed’ GOP is better for random
access and synchronous files.
• Each GOP should contain a Sequence
header.
• Files should start on a Sequence header.


Audio Compression

• MediaSonic currently only support Dolby
AC3 Audio streams.
• The standard allows for other types of
audio including MPEG layer 2 audio that is
created by some software encoders
(Heuris).
• AC3 packets are 32msec long.


AC3 Audio

• A compression scheme that can carry
anything from mono to 5.1 surround
sound. We typically use it in either stereo
or 5.1.
• The stereo output plays back a mix of the
AC, although we usually only encode
stereo since HW encoders don’t support
surround sound.


Audio – Things to remember.
• AC3 is the only supported
audio format.
• Audio needs to be encoded
at 384kbits.
• Audio needs to be sampled
at 48kHzs.
• AC3 can only exist as
complete packets of 32
msecs.

Multiplexing

• Wraps the audio and video into a single
stream, in our case a Transport stream.

Audio
Elementary

Video
Elementary

Time


Multiplexing
• Data is packed into 188 byte packets each
starting with a h47.
• A well made file should start and end on packet
boundaries.
• Files can be viewed with a Hex viewer to check.
Start of packet

47 40 11 11 00 00 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00
00 01 B3 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00 13 3B F4
EB E6 F1 1B F4 EB 9F 00 01 B3 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF
FF FF FF 00 13 3B F4 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00 00 01
B3 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00 13 3B F4 EB E6
F1 1B F4 EB 9F 00 01 B3 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 FF FF 01 B5 20 1E 47 00 11 12

Start of Seq. head
End of packet


Mux – Things to remember.

• Mux is Transport and uses 188 byte
packets.
• Mux data rate must allow for the Video +
Audio + Overhead.
• Audio should be shorter than video.
• File should and start and end on packet
boundaries.


Software Encoders
• There are two prominent encoders available
– PixleTools - MPEGRepair.
• Picture only.
• Takes 24 bit/pixel graphic files only (BMP or TGA).
• Easy to use & reliable.
• Makes 4.2.0 or 4.2.2 files (our player auto detect and play).
• Has a ‘bug’ that adds a stream terminator incorrectly in the
built in multiplexer (used to make video only transport
streams).
– Heuris - MPP2.
• Picture only or + MPEG audio (unsupported).
• Takes AVI and QuickTime files (with audio).
• Can window into source image.
• Can take images directly from film scanners.

Software Encoders

• Make files with clean start. They include a
Sequence header and first frame is always an I
frame.
• Make files with clean end. It is possible to make
clean looping files.
– Frame count = (GOP size) x N for clean looping files.
• Very good for 3D work.
• MPEGRepair video only files must be trimmed
before use!


Real-time Encoders

• Designed to stream ASI data to a
transmission system.
• Data can be captured asynchronously but
will need ‘trimmed’ for quality playback.
• Some can be switched from ‘Video Off’ to
‘Video On’ creating a Sequence header
and predictable I frame.
• Can make AC3 & MPEG2 audio.
– Typically Left & Right + back up L & R.

Software Multiplexers

• Manzaneta - MP2TSME
– Very flexible DOS based tool. A b**** to use.
• PixelTools – Transmux
– Easy Windows tool but no video only option.

• Both use the same Manzanita engine for
Transport streams.


MPEG for Large Screens

• MPEG uses motion prediction in B and P
frames!
• MPEG encoding looses high frequencies!
• 4.2.0 can resolve horizontal color if there
are 2+ similar colored pixels in a row and
vertical color if there are 2+ pixels in a
column!


MPEG for Large Screens

• SD can be up-res’d to HD giving a better
image than SD alone.
• This allows higher bitrates than the current
SD Players.
• Allows for small GOP’s that better deal
with fast motion vectors.


Orlando Moreno
omoreno@hotmail.com
408.656.2498


Mpeg For The Media Sonic Players

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