RFC relevance of component

As per Relevance of the word component, we have this rfc below:

Network Working Group L.
Request for Comments: 2035 Digital Equipment
Category: Standards Track W.
Xerox
R.
Xerox
S.
Lawrence Berkeley
October 1996

RTP Payload Format for JPEG-compressed

Status of this

This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited

This memo describes the RTP payload format for JPEG video streams
The packet format is optimized for real-time video streams
codec parameters change rarely from frame to frame

This document is a product of the Audio-Video Transport working
within the Internet Engineering Task Force. Comments are
and should be addressed to the working group's mailing list at rem
conf@es.net and/or the author(s).

1.

The Joint Photographic Experts Group (JPEG) standard [1,2,3]
a family of compression algorithms for continuous-tone, still images
This still image compression standard can be applied to video
compressing each frame of video as an independent still image
transmitting them in series. Video coded in this fashion is
called Motion-JPEG

We first give an overview of JPEG and then describe the
subset of JPEG that is supported in RTP and the mechanism by
JPEG frames are carried as RTP payloads

The JPEG standard defines four modes of operation: the sequential
mode, the progressive DCT mode, the lossless mode, and
hierarchical mode. Depending on the mode, the image is

Berc, et. al. Standards Track [Page 1]

RFC 2035 RTP Payload Format for JPEG Video October 1996

in one or more passes. Each pass (called a frame in the
standard) is further broken down into one or more scans. Within
scan, there are one to four components,which represent the
components of a color signal (e.g., "red, green, and blue", or
luminance signal and two chromanince signals). These components
be encoded as separate scans or interleaved into a single scan

Each frame and scan is preceded with a header containing
definitions for compression parameters like quantization tables
Huffman coding tables. The headers and optional parameters
identified with "markers" and comprise a marker segment; each
appears as an entropy-coded bit stream within two marker segments
Markers are aligned to byte boundaries and (in general) cannot
in the entropy-coded segment, allowing scan boundaries to
determined without parsing the bit stream

Compressed data is represented in one of three formats:
interchange format, the abbreviated format, or the table
specification format. The interchange format contains
for all the table used in the by the entropy-coded segments,
the abbreviated format might omit some assuming they were
out-of-band or by a "previous" image

The JPEG standard does not define the meaning or format of
components that comprise the image. Attributes like the color
and pixel aspect ratio must be specified out-of-band with respect
the JPEG bit stream. The JPEG File Interchange Format (JFIF) [4]
a defacto standard that provides this extra information using
application marker segment (APP0). Note that a JFIF file is simply
JPEG interchange format image along with the APP0 segment. In
case of video, additional parameters must be defined out-of-
(e.g., frame rate, interlaced vs. non-interlaced, etc.).

While the JPEG standard provides a rich set of algorithms
flexible compression, cost-effective hardware implementations of
full standard have not appeared. Instead, most hardware JPEG
codecs implement only a subset of the sequential DCT mode
operation. Typically, marker segments are interpreted in
(which "re-programs" the hardware) and the hardware is presented
a single, interleaved entropy-coded scan represented in the YUV
space

2. JPEG Over

To maximize interoperability among hardware-based codecs, we
the sequential DCT operating mode [1,Annex F] and restrict the set
predefined RTP/JPEG "type codes" (defined below) to single-scan
interleaved images. While this is more restrictive than

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RFC 2035 RTP Payload Format for JPEG Video October 1996

baseline JPEG, many hardware implementation fall short of
baseline specification (e.g., most hardware cannot decode non
interleaved scans).

In practice, most of the table-specification data rarely changes
frame to frame within a single video stream. Therefore, RTP/
data is represented in abbreviated format, with all of the
omitted from the bit stream. Each image begins immediately with
(single) entropy-coded scan. The information that would otherwise
in both the frame and scan headers is represented entirely within
64-bit RTP/JPEG header (defined below) that lies between the
header and the JPEG scan and is present in every packet

While parameters like Huffman tables and color space are likely
remain fixed for the lifetime of the video stream, other
should be allowed to vary, notably the quantization tables and
size (e.g., to implement rate-adaptive transmission or allow a
to adjust the "quality level" or resolution manually). Thus
fields in the RTP/JPEG header are allocated to represent
information. Since only a small set of quantization tables
typically used, we encode the entire set of quantization tables in
small integer field. The image width and height are
explicitly

Because JPEG frames are typically larger than the
network's maximum packet size, frames must often be fragmented
several packets. One approach is to allow the network layer
RTP (e.g., IP) to perform the fragmentation. However, this
rate-controlling the resulting packet stream or partial delivery
the presence of loss. For example, IP will not deliver a
datagram to the application if one or more fragments is lost, or
might fragment an 8000 byte frame into a burst of 8 back-to-
packets. Instead, RTP/JPEG defines a simple fragmentation
reassembly scheme at the RTP level

3. RTP/JPEG Packet

The RTP timestamp is in units of 90000Hz. The same timestamp
appear across all fragments of a single frame. The RTP marker bit
set in the last packet of a frame

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RFC 2035 RTP Payload Format for JPEG Video October 1996

3.1. JPEG

A special header is added to each packet that immediately follows
RTP header

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type specific | Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Q | Width | Height |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.1.1. Type specific: 8

Interpretation depends on the value of the type field

3.1.2. Fragment Offset: 24

The Fragment Offset is the data offset in bytes of the current
in the JPEG scan

3.1.3. Type: 8

The type field specifies the information that would otherwise
present in a JPEG abbreviated table-specification as well as
additional JFIF-style parameters not defined by JPEG. Types 0-127
are reserved as fixed, well-known mappings to be defined by
document and future revisions of this document. Types 128-255
free to be dynamically defined by a session setup protocol (which
beyond the scope of this document).

3.1.4. Q: 8

The Q field defines the quantization tables for this frame using
algorithm that determined by the Type field (see below).

3.1.5. Width: 8

This field encodes the width of the image in 8-pixel multiples (e.g.,
a width of 40 denotes an image 320 pixels wide).

3.1.6. Height: 8

This field encodes the height of the image in 8-pixel
(e.g., a height of 30 denotes an image 240 pixels tall).

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RFC 2035 RTP Payload Format for JPEG Video October 1996

3.1.7.

The data following the RTP/JPEG header is an entropy-coded
consisting of a single scan. The scan header is not present and
inferred from the RTP/JPEG header. The scan is terminated
implicitly (i.e., the point at which the image is fully parsed),
explicitly with an EOI marker. The scan may be padded to
length with undefined bytes. (Existing hardware codecs
extra lines at the bottom of a video frame and removal of these
would require a Huffman-decoding pass over the data.)

As defined by JPEG, restart markers are the only type of marker
may appear embedded in the entropy-coded segment. The "type code
determines whether a restart interval is defined, and
whether restart markers may be present. It also determines if
restart intervals will be aligned with RTP packets, allowing
partial decode of frames, thus increasing resiliance to packet drop
If restart markers are present, the 6-byte DRI segment (
restart interval marker [1, Sec. B.2.4.4] precedes the scan).

JPEG markers appear explicitly on byte aligned boundaries
with an 0xFF. A "stuffed" 0x00 byte follows any 0xFF byte
by the entropy coder [1, Sec. B.1.1.5].

4.

4.1. The Type

The Type field defines the abbreviated table-specification
additional JFIF-style parameters not defined by JPEG, since they
not present in the body of the transmitted JPEG data. The Type
must remain constant for the duration of a session

Six type codes are currently defined. They correspond to
abbreviated table-specification indicating the "Baseline
sequential" mode, 8-bit samples, square pixels, three components
the YUV color space, standard Huffman tables as defined in [1,
K.3], and a single interleaved scan with a scan component
indicating components 0, 1, and 2 in that order. The Y, U, and
color planes correspond to component numbers 0, 1, and 2,
respectively. Component 0 (i.e., the luminance plane) uses
table number 0 and quantization table number 0 (defined below)
components 1 and 2 (i.e., the chrominance planes) use Huffman
number 1 and quantization table number 1 (defined below).

Additionally, video is non-interlaced and unscaled (i.e., the
ratio is determined by the image width and height). The frame
is variable and explicit via the RTP timestamp

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RFC 2035 RTP Payload Format for JPEG Video October 1996

Six RTP/JPEG types are currently defined that assume all of
above. The odd types have different JPEG sampling factors from
even ones

horizontal
types comp samp. fact. samp. fact
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0/2/4 | 0 | 2 | 1 |
| 0/2/4 | 1 | 1 | 1 |
| 0/2/4 | 2 | 1 | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1/3/5 | 0 | 2 | 2 |
| 1/3/5 | 1 | 1 | 1 |
| 1/3/5 | 2 | 1 | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

These sampling factors indicate that the chromanince components
type 0/2/4 video is downsampled horizontally by 2 (often
4:2:2) while the chrominance components of type 1/3/5 video
downsampled both horizontally and vertically by 2 (often
4:2:0).

The three pairs of types (0/1), (2/3) and (4/5) differ from
other as follows

0/1 : No restart markers are present in the entropy data
No restriction is placed on the fragmentation of the
into RTP packets
The type specific field is unused and must be zero

2/3 : Restart markers are present in the entropy data
The entropy data is preceded by a DRI marker segment,
the restart interval
No restriction is placed on the fragmentation of the
into RTP packets
The type specific field is unused and must be zero

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RFC 2035 RTP Payload Format for JPEG Video October 1996

4/5 : Restart markers are present in the entropy data
The entropy data is preceded by a DRI marker segment,
the restart interval
Restart intervals are be sent as separate (possibly multiple
RTP packets
The type specific field (TSPEC) is used as follows
A restart interval count (RCOUNT) is defined,
starts at zero, and is incremented for each
interval in the frame

The first packet of a restart interval gets TSPEC = RCOUNT
Subsequent packets of the restart interval get TSPEC = 254,
except the final packet, which gets TSPEC = 255.

Additional types in the range 128-255 may be defined by
means, such as a session protocol

Appendix B contains C source code for transforming the RTP/
header parameters into the JPEG frame and scan headers that
absent from the data payload

4.2. The Q

The quantization tables used in the decoding process
algorithmically derived from the Q field. The algorithm used
on the type field but only one algorithm is currently defined for
two types

Both type 0 and type 1 JPEG assume two quantizations tables.
tables are chosen as follows. For 1 <= Q <= 99, the Independent
Group's formula [5] is used to produce a scale factor S as

S = 5000 / Q for 1 <= Q <= 50
= 200 - 2 * Q for 51 <= Q <= 99

This value is then used to scale Tables K.1 and K.2 from [1]
(saturating each value to 8-bits) to give quantization table
0 and 1, respectively. C source code is provided in Appendix A
compute these tables

For Q >= 100, a dynamically defined quantization table is used,
might be specified by a session setup protocol. (This
protocol is beyond the scope of this document). It is expected
the standard quantization tables will handle most cases in practice
and dynamic tables will be used rarely. Q = 0 is reserved

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RFC 2035 RTP Payload Format for JPEG Video October 1996

4.3. Fragmentation and

Since JPEG frames are large, they must often be fragmented.
should be fragmented into packets in a manner avoiding
at a lower level. When using restart markers, frames should
fragmented such that each packet starts with a restart interval (
below).

Each packet that makes up a single frame has the same timestamp.
fragment offset field is set to the byte offset of this packet
the original frame. The RTP marker bit is set on the last packet
a frame

An entire frame can be identified as a sequence of packets
with a packet having a zero fragment offset and ending with a
having the RTP marker bit set. Missing packets can be
either with RTP sequence numbers or with the fragment offset
lengths of each packet. Reassembly could be carried out without
offset field (i.e., using only the RTP marker bit and
numbers), but an efficient single-copy implementation would
otherwise be possible in the presence of misordered packets
Moreover, if the last packet of the previous frame (containing
marker bit) were dropped, then a receiver could not detect that
current frame is entirely intact

4.4. Restart

Restart markers indicate a point in the JPEG stream at which
Huffman codec and DC predictors are reset, allowing partial
starting at that point. The use of restart markers allows
robustness in the face of packet loss

RTP/JPEG Types 4/5 allow for partial decode of frames, due to
alignment of restart intervals with RTP packets. The decoder knows
has a whole restart interval when it gets sequence of packets
contiguous RTP sequence numbers, starting with TSPEC<254 (RCOUNT)
either ending with TSPEC==255, or TSPEC<255 and next packet'
TSPEC<254 (or end of frame).

It can then decompress the RST interval, and paint it. The X and
tile offsets of the first MCU in the interval are given by

tile_offset = RCOUNT * restart_interval * 2
x_offset = tile_offset % frame_width_in_
y_offset = tile_offset / frame_width_in_

The MCUs in a restart interval may span multiple tile rows

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RFC 2035 RTP Payload Format for JPEG Video October 1996

Decoders can, however, treat types 4/5 as types 2/3,
reassembling the entire frame and then decoding

5. Security

Security issues are not discussed in this memo

6. Authors'

Lance M.
Systems Research
Digital Equipment
130 Lytton
Palo Alto CA 94301

Phone: +1 415 853 2100
EMail: berc@pa.dec.

William C.
Xerox
3333 Coyote Hill
Palo Alto, CA 94304

Phone: +1 415 812 4816
EMail: fenner@cmf.nrl.navy.

Ron
Xerox
3333 Coyote Hill
Palo Alto, CA 94304

Phone: +1 415 812 4459
EMail: frederick@parc.xerox.

Steven
Lawrence Berkeley
M/S 46A-1123
One Cyclotron
Berkeley, CA 94720

Phone: +1 510 486 7520
EMail: mccanne@ee.lbl.

Berc, et. al. Standards Track [Page 9]

RFC 2035 RTP Payload Format for JPEG Video October 1996

7.

[1] ISO DIS 10918-1. Digital Compression and Coding of Continuous-
Still Images (JPEG), CCITT Recommendation T.81.

[2] William B. Pennebaker, Joan L. Mitchell, JPEG: Still Image
Compression Standard, Van Nostrand Reinhold, 1993.

[3] Gregory K. Wallace, The JPEG Sill Picture Compression Standard
Communications of the ACM, April 1991, Vol 34, No. 1, pp. 31-44.

[4] The JPEG File Interchange Format. Maintained by C-Cube Microsys
tems, Inc., and available
ftp://ftp.uu.net/graphics/jpeg/jfif.ps.gz

[5] Tom Lane et. al., The Independent JPEG Group software JPEG codec
Source code available
ftp://ftp.uu.net/graphics/jpeg/jpegsrc.v5.tar.gz

Berc, et. al. Standards Track [Page 10]

RFC 2035 RTP Payload Format for JPEG Video October 1996

Appendix

The following code can be used to create a quantization table from
Q factor

/*
* Table K.1 from JPEG spec
*/
static const int jpeg_luma_quantizer[64] = {
16, 11, 10, 16, 24, 40, 51, 61,
12, 12, 14, 19, 26, 58, 60, 55,
14, 13, 16, 24, 40, 57, 69, 56,
14, 17, 22, 29, 51, 87, 80, 62,
18, 22, 37, 56, 68, 109, 103, 77,
24, 35, 55, 64, 81, 104, 113, 92,
49, 64, 78, 87, 103, 121, 120, 101,
72, 92, 95, 98, 112, 100, 103, 99
};

/*
* Table K.2 from JPEG spec
*/
static const int jpeg_chroma_quantizer[64] = {
17, 18, 24, 47, 99, 99, 99, 99,
18, 21, 26, 66, 99, 99, 99, 99,
24, 26, 56, 99, 99, 99, 99, 99,
47, 66, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99
};

/*
* Call MakeTables with the Q factor and two int[64] return
*/

MakeTables(int q, u_char *lum_q, u_char *chr_q

int i
int factor = q

if (q < 1) factor = 1;
if (q > 99) factor = 99;
if (q < 50)
q = 5000 / factor

q = 200 - factor*2;

Berc, et. al. Standards Track [Page 11]

RFC 2035 RTP Payload Format for JPEG Video October 1996

for (i=0; i < 64; i++) {
int lq = ( jpeg_luma_quantizer[i] * q + 50) / 100;
int cq = ( jpeg_chroma_quantizer[i] * q + 50) / 100;

/* Limit the quantizers to 1 <= q <= 255 */
if ( lq < 1) lq = 1;
else if ( lq > 255) lq = 255;
lum_q[i] = lq

if ( cq < 1) cq = 1;
else if ( cq > 255) cq = 255;
chr_q[i] = cq
}

Appendix

The following routines can be used to create the JPEG marker
corresponding to the table-specification data that is absent from
RTP/JPEG body

u_char lum_dc_codelens[] = {
0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0,
};

u_char lum_dc_symbols[] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
};

u_char lum_ac_codelens[] = {
0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d
};

u_char lum_ac_symbols[] = {
0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,
0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08,
0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0,
0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16,
0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28,
0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,
0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,

Berc, et. al. Standards Track [Page 12]

RFC 2035 RTP Payload Format for JPEG Video October 1996

0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6,
0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5,
0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4,
0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2,
0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea
0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
0xf9, 0xfa
};

u_char chm_dc_codelens[] = {
0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,
};

u_char chm_dc_symbols[] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
};

u_char chm_ac_codelens[] = {
0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77,
};

u_char chm_ac_symbols[] = {
0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,
0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,
0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,
0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0,
0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34,
0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26,
0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38,
0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96,
0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5,
0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4,
0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3,
0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2,
0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda
0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9,
0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
0xf9, 0xfa
};

u_char *
MakeQuantHeader(u_char *p, u_char *qt, int tableNo

Berc, et. al. Standards Track [Page 13]

RFC 2035 RTP Payload Format for JPEG Video October 1996

*p++ = 0xff
*p++ = 0xdb; /* DQT */
*p++ = 0; /* length msb */
*p++ = 67; /* length lsb */
*p++ = tableNo
memcpy(p, qt, 64);
return (p + 64);

u_char *
MakeHuffmanHeader(u_char *p, u_char *codelens, int ncodes, u_char *symbols
int nsymbols, int tableNo, int tableClass

*p++ = 0xff
*p++ = 0xc4; /* DHT */
*p++ = 0; /* length msb */
*p++ = 3 + ncodes + nsymbols; /* length lsb */
*p++ = tableClass << 4 | tableNo
memcpy(p, codelens, ncodes);
p += ncodes
memcpy(p, symbols, nsymbols);
p += nsymbols
return (p);

/*
* Given an RTP/JPEG type code, q factor, width, and height
* generate a frame and scan headers that can be
* to the RTP/JPEG data payload to produce a JPEG
* image in interchange format (except for possible
* garbage and absence of an EOI marker to terminate the scan).
*/
int MakeHeaders(u_char *p, int type, int q, int w, int h

u_char *start = p
u_char lqt[64];
u_char cqt[64];

/* convert from blocks to pixels */
w <<= 3;
h <<= 3;

MakeTables(q, lqt, cqt);

*p++ = 0xff
*p++ = 0xd8; /* SOI */

p = MakeQuantHeader(p, lqt, 0);

Berc, et. al. Standards Track [Page 14]

RFC 2035 RTP Payload Format for JPEG Video October 1996

p = MakeQuantHeader(p, cqt, 1);

p = MakeHuffmanHeader(p, lum_dc_codelens
sizeof(lum_dc_codelens),
lum_dc_symbols
sizeof(lum_dc_symbols), 0, 0);
p = MakeHuffmanHeader(p, lum_ac_codelens
sizeof(lum_ac_codelens),
lum_ac_symbols
sizeof(lum_ac_symbols), 0, 1);
p = MakeHuffmanHeader(p, chm_dc_codelens
sizeof(chm_dc_codelens),
chm_dc_symbols
sizeof(chm_dc_symbols), 1, 0);
p = MakeHuffmanHeader(p, chm_ac_codelens
sizeof(chm_ac_codelens),
chm_ac_symbols
sizeof(chm_ac_symbols), 1, 1);

*p++ = 0xff
*p++ = 0xc0; /* SOF */
*p++ = 0; /* length msb */
*p++ = 17; /* length lsb */
*p++ = 8; /* 8-bit precision */
*p++ = h >> 8; /* height msb */
*p++ = h; /* height lsb */
*p++ = w >> 8; /* width msb */
*p++ = w; /* wudth lsb */
*p++ = 3; /* number of components */
*p++ = 0; /* comp 0 */
if (type == 0)
*p++ = 0x21; /* hsamp = 2, vsamp = 1 */

*p++ = 0x22; /* hsamp = 2, vsamp = 2 */
*p++ = 0; /* quant table 0 */
*p++ = 1; /* comp 1 */
*p++ = 0x11; /* hsamp = 1, vsamp = 1 */
*p++ = 1; /* quant table 1 */
*p++ = 2; /* comp 2 */
*p++ = 0x11; /* hsamp = 1, vsamp = 1 */
*p++ = 1; /* quant table 1 */

*p++ = 0xff
*p++ = 0xda; /* SOS */
*p++ = 0; /* length msb */
*p++ = 12; /* length lsb */
*p++ = 3; /* 3 components */
*p++ = 0; /* comp 0 */

Berc, et. al. Standards Track [Page 15]

RFC 2035 RTP Payload Format for JPEG Video October 1996

*p++ = 0; /* huffman table 0 */
*p++ = 1; /* comp 1 */
*p++ = 0x11; /* huffman table 1 */
*p++ = 2; /* comp 2 */
*p++ = 0x11; /* huffman table 1 */
*p++ = 0; /* first DCT coeff */
*p++ = 63; /* last DCT coeff */
*p++ = 0; /* sucessive approx. */

return (p - start);
};

Berc, et. al. Standards Track [Page 16]

if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.

RFC documents can be found at I.E.T.F.

Relevance System Copyright © 2002 Spectrum WorldResearch
other technical nosh by ServerMasters Corporation
collaboration of BobX