谁知道 .rm 的文件结构？(50分)

要详细一些的，我已经通过 UDP 取到了RealServer的媒体流，不知道如何存成文件
有知道的，帮帮忙！

Internet Draft Rahul Agarwal, RealNetworks
draft-heftagaub-rmff-00.txt Jeff Ayars, RealNetworks
Brad Hefta-Gaub, RealNetworks
Dale Stammen, RealNetworks
March 13, 1998 Expires: August 13, 1998

RealMedia File Format

STATUS OF THIS MEMO

Thisdo
cument is an Internet-Draft. Internet-Drafts are working
do
cuments of the Internet Engineering Task Force (IETF), its areas, and
its working groups. Note that other groups may also distribute working
do
cuments as Internet-Drafts.

Internet-Drafts are draftdo
cuments valid for a maximum of six months
and may be updated, replaced, or obsoleted by otherdo
cuments at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as ``work in progress''.

To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast).

Distribution of thisdo
cument is unlimited.

Abstract:

Introduction

The RealMedia File Format (RMFF) is designed to be a generic container
for streaming media data. This data may then
be played back locally or
streamed over a network using protocols such as RTSP and RTP. The
format is data-independent, allowing any data type to be recorded,
manipulated and played back.

Note: Thisdo
cument is intended to be informational in nature of what
the file format in use by RealNetworks' RealServer and RealPlayer
implementations. Though we think that there are a lot of important
concepts embodied in this specification, and that it may even make the
basis of a "standard" file format, this is intended to eventually end
up as an Informational RFC.

Copyright Notice:

Copyright (C) RealNetworks (1998). All Rights Reserved.







R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 1
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


RealMedia File Format (RMFF)

1. File Format
2. Header Section
2.1 RealMedia File Header
2.2 Properties Header
2.3 Media Properties Header
2.4 Content Description Header
3. Data Section
3.1 Data Chunk Header
3.2 Data Packet Header
4. Index Section
4.1 Index Section Header
4.2 Index Record

1. File Format

RealMedia File Format is a standard tagged file format that uses
four-character codes to identify file elements. These codes are 32-bit,
represented by a sequence of one to four ASCII alphanumeric characters,
padded on the right with space characters. The data type for
four-character codes is FOURCC. Use the PN_FOURCC macro to convert four
characters into a four-character code.

The basic building block of a RealMedia File is a chunk, which is a
logical unit of data, such as a stream header or a packet of data. Each
chunk contains the following fields:

* four-character code specifying the chunk identifier
* 32-bit value specifying the size of the data member in the chunk
* blob of opaque chunk data


















R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 2
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


Depending on its type, a top-level chunk can contain subobjects. This
do
cument describes the tagged chunks contained in RMFF, as well as the
format of the data stored in each type of tagged chunk.

Tagged Chunk +----------------------+
| ID |
+----------------------+
| Size |
+----------------------+
| Data |
Tagged Chunk +----------------------+
| ID |
+----------------------+
| Size |
+----------------------+
| |
/+-------------+ |
Subchunk / | Data | |
/ | | |
/| | |
/+-------------+ |
Subchunk / | Data | |
/ | | |
/| | |
+-------------+ |
+----------------------+
Figure 1. Tagged File Formats

2. Header Section

Because RMFF is a tagged file format, the order of the chunks is not
explicit, except that the RealMedia File Header must be the first chunk
in the file. However, most applications write the standard headers into
the file's header section. The following chunks are typically found in
the header section of RMFF:

* RealMedia File Header (This must be the first chunk of the file)
* Properties Header
* Media Properties Header
* Content Description Header

After the RealMedia File Header object, the other headers may appear in
any order. All headers are required except the Index Header. The
following sections describe the individual header objects ,





R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 3
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


2.1 RealMedia File Header

Each RealMedia file begin
s with the RealMedia File Header, which
identifies the file as RMFF. There is only one RealMedia File Header in
a RealMedia file. Because the contents of the RealMedia File Header may
change with different versions of RMFF, the header structure supports an
object version field for determining what additional fields exists. The
following pseudo-structure describes the RealMedia File Header:

RealMedia_File_Header
{
UINT32 object_id;
UINT32 size;
UINT16 object_version;

if (object_version == 0)
{
UINT32 file_version;
UINT32 num_headers;
}
}

The RealMedia File Header contains the following fields:

object_id: 32 bits
The unique object ID for a RealMedia File ('.RMF'). All RealMedia
files begin
with this identifier.

size: 32 bits
The size of the RealMedia header section in bytes.

object_version: 16 bits
The version of the RealMedia File Header object. All files created
according to this specification have an object_version number of 0
(zero).

file_version: 32 bits
The version of the RealMedia file in PN Version format. All files
created according to this specification have a major version number
of 1. This member is present on all RealMedia_File_Header objects
with an object_version of 0 (zero).

num_headers: 32 bits
The number of headers in the header section that follow the
RealMedia File Header. This member is present on all
RealMedia_File_Header objects with an object_version of 0 (zero).



R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 4
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


2.2 Properties Header

The Properties Header describes the general media properties of the
RealMedia File. Components of the RealMedia system use this object to
configure themselves for handling the data in the RealMedia file or
stream. There is only one Properties Header in a RealMedia file. The
following pseudo-structure describes the Properties header:

Properties
{
UINT32 object_id;
UINT32 size;
UINT16 object_version;

if (object_version == 0)
{
UINT32 max_bit_rate;
UINT32 avg_bit_rate;
UINT32 max_packet_size;
UINT32 avg_packet_size;
UINT32 num_packets;
UINT32 duration;
UINT32 preroll;
UINT32 index_offset;
UINT32 data_offset;
UINT16 num_streams;
UINT16 flags;
}
}

The Properties Header contains the following fields:

object_id: 32 bits
The unique object ID for a Properties Header ('PROP').

size: 32 bits
The size of the Properties Header in bytes.

object_version: 16 bits
The version of the RealMedia File Header object. All files created
according to this specification have an object_version number of 0
(zero).







R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 5
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


max_bit_rate: 32 bits
The maximum bit rate required to deliver this file over a network.
This member is present on all Properties objects with an
object_version of 0 (zero).

avg_bit_rate: 32 bits
The average bit rate required to deliver this file over a network.
This member is present on all Properties objects with an
object_version of 0 (zero).

max_packet_size: 32 bits
The largest packet size (in bytes) in the media data. This member is
present on all Properties objects with an object_version of 0 (zero).

avg_packet_size: 32 bits
The average packet size (in bytes) in the media data. This member
is present on all Properties objects with an object_version of 0
(zero).

num_packets: 32 bits
The number of packets in the media data. This member is present on
all Properties objects with an object_version of 0 (zero).

duration: 32 bits
The duration of the file in milliseconds. This member is present on
all Properties objects with an object_version of 0 (zero).

preroll: 32 bits
The number of milliseconds to pre-buffer before starting playback.
This member is present on all Properties objects with an
object_version of 0 (zero).

index_offset: 32 bits
The offset in bytes from the start of the file to the start of the
index header object. This member is present on all Properties
objects with an object_version of 0 (zero).

data_offset: 32 bits
The offset in bytes from the start of the file to the start of the
Data Section. This member is present on all Properties objects with
an object_version of 0 (zero).

num_streams: 16 bits
The number of media streams contained in the file. This member is
present on all Properties objects with an object_version of 0
(zero).



R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 6
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


flags: 16 bits
Flags indicating characteristics of the RealMedia file. The
following flags are defined:

o #define PN_SAVE_ENABLED 0x0001

Allows clients to save a copy of the RealMedia file to disk.

o #define PN_PERFECT_PLAY_ENABLED 0x0002

Allows clients to use extra buffering to ensure Perfect Play.

o #define PN_LIVE_BROADCAST 0x0004

The RealMedia file is being generated by a live broadcast.

2.3 Media Properties Header

The Media Properties Header describes the specific media properties of
each stream in a RealMedia File. Components of the RealMedia system use
this object to configure themselves for handling the media data in each
stream. There is one Media Properties Header for each media stream in a
RealMedia file. The following pseudo-structure describes the Media
Properties header:

Media_Properties
{
UINT32 object_id;
UINT32 size;
UINT16 object_version;



















R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 7
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


if (object_version == 0)
{
UINT16 stream_number;
UINT32 max_bit_rate;
UINT32 avg_bit_rate;
UINT32 max_packet_size;
UINT32 avg_packet_size;
UINT32 start_time;
UINT32 preroll;
UINT32 duration;
UINT8 stream_name_size;
UINT8[stream_name_size] stream_name;
UINT8 mime_type_size;
UINT8[mime_type_size] mime_type;
UINT32 type_specific_len;
UINT8[type_specific_len] type_specific_data;
}
}

The Media Properties Header contains the following fields:

object_id: 32 bits
The unique object ID for a Media Properties Header ('MDPR').

size: 32 bits
The size of the Media Properties Header in bytes.

object_version: 16 bits
The version of the Media Properties Header object.

stream_number: 32 bits
The stream_number (synchronization source identifier) is a unique
value that identifies a media stream. Every data packet that
belongs to a media stream contains the same STREAM_NUMBER. The
STREAM_NUMBER enables a receiver of multiple media streams to
distinguish which packets belong to each media stream. This member
is present on all MediaProperties objects with an object_version of
0 (zero).

max_bit_rate: 32 bits
The maximum bit rate required to deliver this stream over a
network. This member is present on all MediaProperties objects
with an object_version of 0 (zero).






R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 8
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


avg_bit_rate: 32 bits
The average bit rate required to deliver this stream over a
network. This member is present on all MediaProperties objects
with an object_version of 0 (zero).

max_packet_size: 32 bits
The largest packet size (in bytes) in the stream of media
data. This member is present on all MediaProperties objects with an
object_version of 0 (zero).

avg_packet_size: 32 bits
The average packet size (in bytes) in the stream of media
data. This member is present on all MediaProperties objects with an
object_version of 0 (zero).

start_time: 32 bits
The time offset in milliseconds to add to the timestamp of each
packet in a media stream. This member is present on all
MediaProperties objects with an object_version of 0 (zero).

preroll: 32 bits
The time offset in milliseconds to subtract to the timestamp of
each packet in a media stream. This member is present on all
MediaProperties objects with an object_version of 0 (zero).

duration: 32 bits
The duration of the stream in milliseconds. This member is present
on all MediaProperties objects with an object_version of 0 (zero).

stream_name_size: 8 bits
The length of the following stream_name field in bytes. This member
is present on all MediaProperties objects with an object_version of
0 (zero).

stream_name: variable length
A non-unique alias or name for the stream. This member is present
on all MediaProperties objects with an object_version of 0 (zero).

mime_type_size: 8 bits
The length of the following mime_type field in bytes. This member
is present on all MediaProperties objects with an object_version of
0 (zero).







R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 9
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


mime_type: variable length
A non-unique MIME style type/subtype string for data associated
with the stream. This member is present on all MediaProperties
objects with an object_version of 0 (zero).

type_specific_len: 32 bits
The length of the following type_specific_data in bytes. The
type_specific_data is typically used by the data-type renderer to
initialize itself in order to process the media stream. This member
is present on all MediaProperties objects with an object_version of
0 (zero).

type_specific_data: variable length
The type_specific_data is typically used by the data-type renderer
to initialize itself in order to process the media stream. This
member is present on all MediaProperties objects with an
object_version of 0 (zero).

2.4 Content Description Header

The Content Description Header contains the title, author, copyright,
and comments information for the RealMedia File. All text data is in
ASCII format. The following pseudo-structure describes the Content
Description Header:

Content_Description
{
UINT32 object_id;
UINT32 size;
UINT16 object_version;

if (object_version == 0)
{
UINT16 title_len;
UINT8[title_len] title;
UINT16 author_len;
UINT8[author_len] author;
UINT16 copyright_len;
UINT8[copyright_len] copyright;
UINT16 comment_len;
UINT8[comment_len] comment;
}
}






R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 10
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


The Content Description Header contains the following fields:

object_id: 32 bits
The unique object ID for the Content Description Header ('CONT').

size: 32 bits
The size of the Content Description Header in bytes.

object_version: 16 bits
The version of the Content Description Header object.

title_len: 16 bits
The length of the title data in bytes. Note that the title data is
not null terminated. This member is present on all Content
Description Header objects with an object_version of 0 (zero).

title: variable length
An array of ASCII characters that represents the title information
for the RealMedia file. This member is present on all Content
Description Header objects with an object_version of 0 (zero).

author_len: 16 bits
The length of the author data in bytes. Note that the author data
is not null terminated. This member is present on all Content
Description Header objects with an object_version of 0 (zero).

author: variable length
An array of ASCII characters that represents the author information
for the RealMedia file. This member is present on all Content
Description Header objects with an object_version of 0 (zero).

copyright_len: 16 bits
The length of the copyright data in bytes. Note that the copyright
data is not null terminated. This member is present on all Content
Description Header objects with an object_version of 0 (zero).

copyright: variable length
An array of ASCII characters that represents the copyright
information for the RealMedia file. This member is present on all
Content Description Header objects with an object_version of 0
(zero).

comment_len: 16 bits
The length of the comment data in bytes. Note that the comment data
is not null terminated. This member is present on all Content
Description Header objects with an object_version of 0 (zero).



R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 11
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


comment: variable length
An array of ASCII characters that represents the comment
information for the RealMedia file. This member is present on all
Content Description Header objects with an object_version of 0
(zero).

3. Data Section

The data section of the RealMedia file consists of a Data Section Header
that describes the contents of the data section, followed by a series of
interleaved media data packets. Note that the size field of the Data
Chunk Header is the size of the entire data chunk, including the media
data packets.

3.1 Data Chunk Header

The Data Chunk Header marks the start of the data chunk. There is
usually only one data chunk in a RealMedia file, however for extremely
large files there may be multiple data chunks. The following
pseudo-structure describes the Data chunk header:

Data_Chunk_Header
{
UINT32 object_id;
UINT32 size;
UINT16 object_version;

if (object_version == 0)
{
UINT32 num_packets;
UINT32 next_data_header;
}
}

The Data Chunk Header contains the following fields:

object_id: 32 bits
The unique object ID for the Data Chunk Header ('DATA').

size: 32 bits
The size of the Data Chunk in bytes.

object_version: 16 bits
The version of the Data Chunk Header object.





R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 12
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


num_packets: 32 bits
Number of packets in the data chunk. This member is present on all
Data Chunk Header objects with an object_version of 0 (zero).

next_data_header: 32 bits
Offset from start of file to the next data chunk. This field is not
typically used. This member is present on all Data Chunk Header
objects with an object_version of 0 (zero).

3.2 Data Packet Header

The data section of a RealMedia file consists of a series of interleaved
data objects. Each data object contains a packet of data for a media
stream. Because a RealMedia file can contain numerous media streams,
data objects for each stream are interleaved. The following
pseudo-structure describes the details of each interleaved packet:

Media_Packet_Header
{
UINT16 object_version;

if (object_version == 0)
{
UINT16 length;
UINT16 stream_number;
UINT32 timestamp;
UINT8 reserved;
UINT8 flags;
UINT8[length] data;
}
}

The Media Packet Header contains the following fields:

object_version: 16 bits
The version of the Media Packet Header object.

length: 16 bits
The length of the packet in bytes. This member is present on all
Media Packet Header objects with an object_version of 0 (zero).

stream_number: 16 bits
The 16-bit alias used to associate data packets with their
associated Media Properties Header. This member is present on all
Media Packet Header objects with an object_version of 0 (zero).




R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 13
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


timeStamp: 32 bits
The timestamp of the packet in milliseconds This member is present
on all Media Packet Header objects with an object_version of 0
(zero).

reserved: 8 bits
This is not used. This member is present on all Media Packet Header
objects with an object_version of 0 (zero).

flags: 16 bits
Flags describing the properties of the packet. The following flags
are defined:

o #define PN_RELIABLE_FLAG 0x0001

If this flag is set, the packet is delivered reliably.

o #define PN_KEYFRAME_FLAG 0x0002

If this flag is set, the packet is part of a key frame or in
some way marks a boundary in your data stream.

This member is present on all Media Packet Header objects with an
object_version of 0 (zero).

data: variable length
The application-specific media data. This member is present on all
Media Packet Header objects with an object_version of 0 (zero).

4. Index Section

The index section of the RealMedia file consists of a Index Chunk Header
that describes the contents of the index section, followed by a series
of index records. Note that the size field of the Index Chunk Header is
the size of the entire index chunk, including the index records.

4.1 Index Section Header

The Index Chunk Header marks the start of the index chunk. There is
usually one index chunk per stream in a RealMedia file. The following
pseudo-structure describes the Index chunk header.








R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 14
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


Index_Chunk_Header
{
u_int32 object_id;
u_int32 size;
u_int16 object_version;

if (object_version == 0)
{
u_int32 num_indices;
u_int16 stream_number;
u_int32 next_index_header;
}
}

The Index Chunk Header contains the following fields:

object_id: 32 bits
The unique object ID for the Index Chunk Header ('INDX').

size: 32 bits
The size of the Index Chunk in bytes.

object_version: 16 bits
The version of the Index Chunk Header object.

num_indices: 32 bits
Number of index records in the index chunk. This member is present
on all Index Chunk Header objects with an object_version of 0
(zero).

stream_number: 16 bits
The stream number for which the index records in this index chunk
are associated. This member is present on all Index Chunk Header
objects with an object_version of 0 (zero).

next_index_header: 32 bits
Offset from start of file to the next index chunk. This field lets
RealMedia file format readers find all the index chunks
quickly. This member is present on all Index Chunk Header objects
with an object_version of 0 (zero).









R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 15
--------------------------------------------------------------------------------
INTERNET-DRAFT RTSP March 13, 1998


4.2 Index Record

The index section of a RealMedia file consists of a series of index
record objects. Each index record contains information for quickly
finding a packet of a particular time stamp for a media stream. The
following pseudo-structure describes the details of each index record:

IndexRecord
{
UINT16 object_version;

if (object_version == 0)
{
u_int32 timestamp;
u_int32 offset;
u_int32 packet_count_for_this_packet;
}
}

An Index Record contains the following fields:

object_version: 16 bits
The version of the Index Record object.

timestamp: 32 bits
The timestamp in milliseconds associated with this record. This
member is present on all Index Record objects with an
object_version of 0 (zero).

offset: 32 bits
The offset from the start of the file at which this packet can be
found. This member is present on all Index Record objects with an
object_version of 0 (zero).

packet_count_for_this_packet: 32 bits
The packet number of the packet for this record. This is the same
number of packets that would have been seen had the file been
played from the begin
ning to this point. This member is present on
all Index Record objects with an object_version of 0 (zero).










R. Agarwal, J. Ayars, B. Hefta-Gaub, D. Stammen Page 16
Original

感谢 datm :
顺便在问一下,RTSP 的对话中有 CompanyID: xxxxxxxxxxxxxxxxx== 之类的信息
象是 Base64 的加密,其密码表是什么？
生成 RealChallenge1: 19459da415c6b4f58e3fd96c4f894e18 的算法有吗？
看来你那资料不少，能给发点吗？
mailto: oops@jn-public.sd.cninfo.net

分好商量！

感谢 datm :
顺便在问一下,RTSP 的对话中有 CompanyID: xxxxxxxxxxxxxxxxx== 之类的信息
象是 Base64 的加密,其密码表是什么？
生成 RealChallenge1: 19459da415c6b4f58e3fd96c4f894e18 的算法有吗？
看来你那资料不少，能给发点吗？

非也，我是在研究ASF格式的时候顺便收集的RM格式资料。（还没看过呢）
有的软件能实现，反编译看看，很头疼的。