Data Stream
Kuliah Multimedia
Who Says What in Which Channel To Whom With What
Effect
Komunikator / Sender
Integrasi
Distribusi
Computer Network /
Telecommunication
Network
Kombinasi
Komunikan / Receiver
Diskrit
Kontinyu
text
audio
gambar
grafik
video
Independesi media
A multimedia system is characterized by
computer-controlled, integrated production,
manipulation, presentation, storage and
communication of independent information,
which is encoded at least through a
continuous (time-independent) and a
discrete (time independent) medium.
Multimedia : Computing, Communication & Applications page 17
Transmisi data
Pada multimedia yang terditribusi
(distributed multimedia/network base
multimedia) data disitribusikan
melalui jaringan transmisi dan
switching.
 Informasi yang ditransmisikan dibagibagi menjadi paket-paket data.

Apa itu Data Stream ?

Data Stream is “A sequence of individual
packet transmitted in a time-dependent
fashion” (suatu barisan paket yang
ditransmisikan dlm modus yang tergantung
waktu)



Sinonim dari Data Stream adalah Data FLow
Paket data (atau disingkat paket atau juga
message/pesan) membawa informasi baik dari
data dalam medium diskrit atau kontinyu
Paket mengindikasikan data sudah dalam
bentuk representasi digital
Representasi Data Stream
D1
D2
D3
D4
D5
Dn
Data stream mengalir dari source ke destinasi
Paket data yang tersusun secara beurutan
Berbentuk sinyal digital
Waktu (t)
Data stream tradisional
Terdapat 3 mode transmisi data stream:
Mode transmisi Asynchronous
1.
•
Refers to events that are not synchronized, or coordinated, in time. The following are
considered asynchronous operations. The interval between transmitting A and B is not the
same as between B and C. The ability to initiate a transmission at either end. The ability to
store and forward messages. Starting the next operation before the current one is completed.
Mode transmisi Synchronous
2.
•
Refers to events that are synchronized, or coordinated, in time. For example, the interval
between transmitting A and B is the same as between B and C, and completing the current
operation before the next one is started are considered synchronous operations.
Mode transmisi Isochronous
3.
•
•
Isochronous transmission transmits asynchronous data over a synchronous data link so
that individual characters are only separated by a whole number of bit-length intervals. An
isochronous message protocol assigns each data source a fixed amount of time to transmit
(its "slot") within each cycle through the sources. That guarantees that each source will have
regular opportunities to transmit the latest information. If a source has no more data to
transmit, then the rest of its time slot is wasted. If it has more to send than will fit in its slot, it
has to either store the excess data and transmit it in its next slot, or discard it.
Isochronous communication suits applications where a steady data stream is more important
than completeness and accuracy, e.g. video conferencing.
http://encyclopedia2.thefreedictionary.com/isochronous
Karakteristik data stream
tradisional
1.
Mode transmisi Asynchronous
•
•
•
•
•
2.
Mode transmisi Synchronous
•
•
•
3.
Tidak ada batasan waktu transmisi paket
Paket yg dikirimkan cepat
Kebanyakah digunakan untuk media diskrit (misalnya: Email,
Ethernet)
Jika digunakan untuk mentransmisikan media kontinyu dapat
dikombinasikan dengan menambahkan pembatasan waktu
Contoh : Modem Asinkron
Maksimum waktu delay end-to-end ditentukan. Manfaatnya
untuk menghindari paket data yang hilang. Setiap pakettidak
memiliki garansi sampai ke penerima.Oleh karena itu perlu
buffer/storage temporer.
Misalnya maksimal data rate video 140 Mbps dan maksimal
delay dalam 1 detik
Contohnya modem Sinkronous (HDLC,SDLC)
Mode transmisi Isochronous
•
Maksimum dan minimum waktu delay end-to-end ditentukan
dan dilakukan garansi pada tiap paket.
http://www.versitron.com/synchronous.htm
http://www.comptechdoc.org/independent/networking/cert/netmodems.html
Mode transmisi Asynchronous
Mode transmisi Syncrhronous
Mode transmisi Isochronous
A
S
Y
N
C
(t)
The interval between transmitting A and S is not the same as between S and Y.
S
Y
N
C
(t)
The interval between transmitting S and Y is the same as between Y and N
I
S
O
(t)
Isochronous transmission transmits asynchronous data over a synchronous data link
Karakteristik data stream pada
media kontinyu
1.
2.
3.
Variasi Interval waktu antar paket (time interval)
•
Strongly periodic
•
Weakly periodic
•
Aperiodic
Variasi besar paket (packet amount / data size)
•
Strongly regular stream
•
Weakly regular stream
•
Irregular stream
Variasi paket yang bersebelahan (contiguous
packet)
•
Continuous stream without intermediate gaps
•
Discrete stream with gaps
Strongly periodic
Weakly periodic
Aperiodic
Contoh : sinyal telepon
Yang dikodekan secara
PCM
T
D1
D2
D3
D4
(t)
Strongly periodic : jika interval antar paket bersifat konstan
T1
D1
D2
T
T2
T1
T3
D3
D4
Contoh : sinyal datastream
Video terkompresi MPEG
T2
D5
D6
(t)
Weakly periodic : jika interval antar paket bersifat konstan hanya
pada waktu terbatas, tetapi dalam waktu keseluruhan tidak konstan
T1
D1
D2
T2
D3
T4
T3
D4
D5
Contoh : sinyal data posisi
Mouse yang ditransmisikan
T5
D6
Aperiodic : Bukan weakly dan bukan pula strongly periodik
(t)
Strongly regular stream
Weakly regular stream
Irregular stream
D1
T
D1
D2
D1
D2
T
D1
t
Strongly regular : jika
Ukuran data (data size)
Konstan untuk seluruh
Paket
Misal : datastream tanpa
kompresi
D3
D2
…..
D3
D1
D3
Dn
t
Weakly regular : jika
Ukuran data paket
(data size) berubah
secara periodik
Misal :datastream Mpeg
t
Irregular : jika
Ukuran data paket
(data size) berubah
secara acak
Continuous stream without intermediate gaps
Discrete stream with gaps
D
D1 D2 D3 D4
…….
Dn
(t)
Continuous stream : paket di transmisikan tanpa ada Gap (disebut
juga dg Connected data)
Misal : ISDN B-channel dengan data audio 64 kbps
T
D
D1 D2
D3
…….
Dn
(t)
Discrete stream : terdapat Gap-gap diantara paket (disebut juga dg
UnConnected data)
Misalnya : transmisi datastraem pada JPEG
Information Units / Satuan informasi

Disebut dengan LDU (Logical Data Unit) :
yaitu informasi yang dianggap paling kecil
dan bermakna, misalnya :



Audio : data sample, grup sample dst
Video : film,clip,frame,block,pixel dst
Jenis LDU berdasarkan durasinya :


Close LDU : durasi ditentukan sebelumnya
(predifined duration), misalnya sampel data
stream audio di dalam komputer
Open LDU : durasi tidak bisa ditentukan
didepan, misalnya :datastream dikirim dari
kamera dan mic menuju komputer
LDU pada data video
FILM
Clip
Frame
Blok
Pixel
Pustaka tambahan



http://encyclopedia2.thefreedictionary.com/isochronous
http://www.versitron.com/synchronous.htm
http://www.comptechdoc.org/independent/networking/cert
/netmodems.html