我有一个RTP Stream插槽，从三星网络摄像机接收JPEG流。
我不太了解JPEG格式的工作原理，但我知道这个传入的JFIF或JPEG流给了我JPEG标题
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type-specific | Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Q | Width | Height |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
and then
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Restart Interval |F|L| Restart Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
and then in the first packet, there is this header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ | Precision | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Quantization Table Data |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
我认为我正确地解析了它们，这是一段代码，我如何存储JPEG Stream数据包。
int extraOff=0;
public bool Decode(byte* data, int offset)
{
if (_initialized == false)
{
type_specific = data[offset + 0];
_frag[0] = data[offset + 3];
_frag[1] = data[offset + 2];
_frag[2] = data[offset + 1];
_frag[3] = 0x0;
fragment_offset = System.BitConverter.ToInt32(_frag, 0);
jpeg_type = data[offset + 4];
q = data[offset + 5];
width = data[offset + 6];
height = data[offset + 7];
_frag[0] = data[offset + 8];
_frag[1] = data[offset + 9];
restart_interval = (ushort)(System.BitConverter.ToUInt16(_frag, 0) & 0x3FF);
if (width == 0) /** elphel 333 full image size more than just one byte less that < 256 **/
width = 256;
byte jpegMBZ = (byte)(data[offset + 12]);
byte jpegPrecision = (byte)(data[offset + 13]);
int jpegLength = (int)((data[offset + 14]) * 256 + data[offset + 15]);
byte[] tableData1 = new byte[64];
byte[] tableData2 = new byte[64];
for (int i = 0; i < 64; ++i)
{
tableData1[i] = data[offset + 16 + i];
tableData2[i] = data[offset + 16+64 + i];
}
byte[] tmp = new byte[1024];
_offset = Utils.MakeHeaders(tmp,jpeg_type, width, height, tableData1, tableData2, 0);
qtable = new byte[_offset];
Array.Copy(tmp, 0, _buffer, 0, _offset);
_initialized = true;
tmp = null;
GC.Collect();
extraOff = jpegLength + 4 ;
}
else
{
_frag[0] = data[15]; //12 + 3
_frag[1] = data[14]; //12 + 2
_frag[2] = data[13]; //12 + 1]
_frag[3] = 0x0;
fragment_offset = System.BitConverter.ToInt32(_frag, 0);
_frag[0] = data[offset + 8];
_frag[1] = data[offset + 9];
restart_interval = (ushort)(System.BitConverter.ToUInt16(_frag, 0) & 0x3FF);
extraOff = 0;
}
return (next_fragment_offset == fragment_offset);
}
public unsafe bool Write(byte* data, int size, out bool sync) //Write(ref byte[] data, int size,out bool sync)
{
if (Decode(data, 12))
{
for (int i = 24 + extraOff; i < size; )
buffer_ptr[_offset++] = data[i++];
size -= 24+extraOff;
next_fragment_offset += size;
sync = true;
return ((data[1] >> 7) == 1);
}
else
{
_initialized = false;
_offset = qtable.Length;
next_fragment_offset = 0;
sync = false;
return false;
}
}
我得到的问题是JPEG文件我成功保存到我的硬盘由于连接JPEG流没有正确显示整个流，所有图像预览器显示第一个两个传入的数据包数据，但剩下的灰色，我相信这意味着，从第三个到最后一个RTP数据包的数据不会被正确解析或保存。
这是我得到的框架 http://rectsoft.net/ideerge/zzz.jpg
size = rawBuffer.Length;
if (sync == true)
{
unsafe
{
fixed (byte* p = rawBuffer)
{
if (_frame.Write(p, size, out sync)) //if (_frame.Write(ref _buffer, size, out sync))
{
// i save my buffer to file here
}
}
}
}
else if ((rawBuffer[1] >> 7) == 1)
{
sync = true;
}
rawBuffer由我的UDP接收功能填充，它的行为与我处理h264流的方式完全相同，看起来像我在VLC上从WIRESHARK捕获的内容100％。
答案 0 :(得分：3)
请参阅我的实施@ https://net7mma.codeplex.com/SourceControl/latest#Rtp/RFC2435Frame.cs
它比上面的实现简单得多，并且如果需要，还有一个RtspClient和RtpClient类
摘录
#region Methods
/// <summary>
/// Writes the packets to a memory stream and creates the default header and quantization tables if necessary.
/// Assigns Image from the result
/// </summary>
internal virtual void ProcessPackets(bool allowLegacyPackets = false)
{
if (!Complete) return;
byte TypeSpecific, Type, Quality;
ushort Width, Height, RestartInterval = 0, RestartCount = 0;
uint FragmentOffset;
//A byte which is bit mapped, each bit indicates 16 bit coeffecients for the table .
byte PrecisionTable = 0;
ArraySegment<byte> tables = default(ArraySegment<byte>);
Buffer = new System.IO.MemoryStream();
//Loop each packet
foreach (RtpPacket packet in m_Packets.Values)
{
//Payload starts at the offset of the first PayloadOctet
int offset = packet.NonPayloadOctets;
if (packet.Extension) throw new NotSupportedException("RFC2035 nor RFC2435 defines extensions.");
//Decode RtpJpeg Header
TypeSpecific = (packet.Payload.Array[packet.Payload.Offset + offset++]);
FragmentOffset = (uint)(packet.Payload.Array[packet.Payload.Offset + offset++] << 16 | packet.Payload.Array[packet.Payload.Offset + offset++] << 8 | packet.Payload.Array[packet.Payload.Offset + offset++]);
#region RFC2435 - The Type Field
/*
4.1. The Type Field
The Type field defines the abbreviated table-specification and
additional JFIF-style parameters not defined by JPEG, since they are
not present in the body of the transmitted JPEG data.
Three ranges of the type field are currently defined. Types 0-63 are
reserved as fixed, well-known mappings to be defined by this document
and future revisions of this document. Types 64-127 are the same as
types 0-63, except that restart markers are present in the JPEG data
and a Restart Marker header appears immediately following the main
JPEG header. Types 128-255 are free to be dynamically defined by a
session setup protocol (which is beyond the scope of this document).
Of the first group of fixed mappings, types 0 and 1 are currently
defined, along with the corresponding types 64 and 65 that indicate
the presence of restart markers. They correspond to an abbreviated
table-specification indicating the "Baseline DCT sequential" mode,
8-bit samples, square pixels, three components in the YUV color
space, standard Huffman tables as defined in [1, Annex K.3], and a
single interleaved scan with a scan component selector indicating
components 1, 2, and 3 in that order. The Y, U, and V color planes
correspond to component numbers 1, 2, and 3, respectively. Component
1 (i.e., the luminance plane) uses Huffman table number 0 and
quantization table number 0 (defined below) and components 2 and 3
(i.e., the chrominance planes) use Huffman table number 1 and
quantization table number 1 (defined below).
Type numbers 2-5 are reserved and SHOULD NOT be used. Applications
based on previous versions of this document (RFC 2035) should be
updated to indicate the presence of restart markers with type 64 or
65 and the Restart Marker header.
The two RTP/JPEG types currently defined are described below:
horizontal vertical Quantization
types component samp. fact. samp. fact. table number
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | 1 (Y) | 2 | 1 | 0 |
| 0, 64 | 2 (U) | 1 | 1 | 1 |
| | 3 (V) | 1 | 1 | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | 1 (Y) | 2 | 2 | 0 |
| 1, 65 | 2 (U) | 1 | 1 | 1 |
| | 3 (V) | 1 | 1 | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
These sampling factors indicate that the chrominance components of
type 0 video is downsampled horizontally by 2 (often called 4:2:2)
while the chrominance components of type 1 video are downsampled both
horizontally and vertically by 2 (often called 4:2:0).
Types 0 and 1 can be used to carry both progressively scanned and
interlaced image data. This is encoded using the Type-specific field
in the main JPEG header. The following values are defined:
0 : Image is progressively scanned. On a computer monitor, it can
be displayed as-is at the specified width and height.
1 : Image is an odd field of an interlaced video signal. The
height specified in the main JPEG header is half of the height
of the entire displayed image. This field should be de-
interlaced with the even field following it such that lines
from each of the images alternate. Corresponding lines from
the even field should appear just above those same lines from
the odd field.
2 : Image is an even field of an interlaced video signal.
3 : Image is a single field from an interlaced video signal, but
it should be displayed full frame as if it were received as
both the odd & even fields of the frame. On a computer
monitor, each line in the image should be displayed twice,
doubling the height of the image.
*/
#endregion
Type = (packet.Payload.Array[packet.Payload.Offset + offset++]);
//Check for a RtpJpeg Type of less than 5 used in RFC2035 for which RFC2435 is the errata
if (!allowLegacyPackets && Type >= 2 && Type <= 5)
{
//Should allow for 2035 decoding seperately
throw new ArgumentException("Type numbers 2-5 are reserved and SHOULD NOT be used. Applications based on RFC 2035 should be updated to indicate the presence of restart markers with type 64 or 65 and the Restart Marker header.");
}
Quality = packet.Payload.Array[packet.Payload.Offset + offset++];
Width = (ushort)(packet.Payload.Array[packet.Payload.Offset + offset++] * 8);// in 8 pixel multiples
Height = (ushort)(packet.Payload.Array[packet.Payload.Offset + offset++] * 8);// in 8 pixel multiples
//It is worth noting Rtp does not care what you send and more tags such as comments and or higher resolution pictures may be sent and these values will simply be ignored.
//Restart Interval 64 - 127
if (Type > 63 && Type < 128)
{
/*
This header MUST be present immediately after the main JPEG header
when using types 64-127. It provides the additional information
required to properly decode a data stream containing restart markers.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Restart Interval |F|L| Restart Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
RestartInterval = (ushort)(packet.Payload.Array[packet.Payload.Offset + offset++] << 8 | packet.Payload.Array[packet.Payload.Offset + offset++]);
RestartCount = (ushort)((packet.Payload.Array[packet.Payload.Offset + offset++] << 8 | packet.Payload.Array[packet.Payload.Offset + offset++]) & 0x3fff);
}
// A Q value of 255 denotes that the quantization table mapping is dynamic and can change on every frame.
// Decoders MUST NOT depend on any previous version of the tables, and need to reload these tables on every frame.
if (/*FragmentOffset == 0 || */Buffer.Position == 0)
{
//RFC2435 http://tools.ietf.org/search/rfc2435#section-3.1.8
//3.1.8. Quantization Table header
/*
This header MUST be present after the main JPEG header (and after the
Restart Marker header, if present) when using Q values 128-255. It
provides a way to specify the quantization tables associated with
this Q value in-band.
*/
if (Quality == 0) throw new InvalidOperationException("(Q)uality = 0 is Reserved.");
else if (Quality >= 100)
{
/* http://tools.ietf.org/search/rfc2435#section-3.1.8
* Quantization Table 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ | Precision | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Quantization Table Data |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
if ((packet.Payload.Array[packet.Payload.Offset + offset++]) != 0)
{
//Must Be Zero is Not Zero
if (System.Diagnostics.Debugger.IsAttached) System.Diagnostics.Debugger.Break();
}
//Read the PrecisionTable (notes below)
PrecisionTable = (packet.Payload.Array[packet.Payload.Offset + offset++]);
#region RFC2435 Length Field
/*
The Length field is set to the length in bytes of the quantization
table data to follow. The Length field MAY be set to zero to
indicate that no quantization table data is included in this frame.
See section 4.2 for more information. If the Length field in a
received packet is larger than the remaining number of bytes, the
packet MUST be discarded.
When table data is included, the number of tables present depends on
the JPEG type field. For example, type 0 uses two tables (one for
the luminance component and one shared by the chrominance
components). Each table is an array of 64 values given in zig-zag
order, identical to the format used in a JFIF DQT marker segment.
* PrecisionTable *
For each quantization table present, a bit in the Precision field
specifies the size of the coefficients in that table. If the bit is
zero, the coefficients are 8 bits yielding a table length of 64
bytes. If the bit is one, the coefficients are 16 bits for a table
length of 128 bytes. For 16 bit tables, the coefficients are
presented in network byte order. The rightmost bit in the Precision
field (bit 15 in the diagram above) corresponds to the first table
and each additional table uses the next bit to the left. Bits beyond
those corresponding to the tables needed by the type in use MUST be
ignored.
*/
#endregion
//Length of all tables
ushort Length = (ushort)(packet.Payload.Array[packet.Payload.Offset + offset++] << 8 | packet.Payload.Array[packet.Payload.Offset + offset++]);
//If there is Table Data Read it from the payload, Length should never be larger than 128 * tableCount
if (Length == 0 && Quality == byte.MaxValue) throw new InvalidOperationException("RtpPackets MUST NOT contain Q = 255 and Length = 0.");
else if (Length > packet.Payload.Count - offset) //If the indicated length is greater than that of the packet taking into account the offset
continue; // The packet must be discarded
//Copy the tables present
tables = new ArraySegment<byte>(packet.Payload.Array, packet.Payload.Offset + offset, (int)Length);
offset += (int)Length;
}
else // Create them from the given Quality parameter ** Duality (Unify Branch)
{
tables = new ArraySegment<byte>(CreateQuantizationTables(Type, Quality, PrecisionTable));
}
//Write the JFIF Header after reading or generating the QTables
byte[] header = CreateJFIFHeader(Type, Width, Height, tables, PrecisionTable, RestartInterval);
Buffer.Write(header, 0, header.Length);
}
//Write the Payload data from the offset
Buffer.Write(packet.Payload.Array, packet.Payload.Offset + offset, packet.Payload.Count - (offset + packet.PaddingOctets));
}
//Check for EOI Marker and write if not found
if (Buffer.Position == Buffer.Length || Buffer.ReadByte() != JpegMarkers.EndOfInformation)
{
Buffer.WriteByte(JpegMarkers.Prefix);
Buffer.WriteByte(JpegMarkers.EndOfInformation);
}
//Create the Image form the Buffer
Image = System.Drawing.Image.FromStream(Buffer);
}