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jimm98yjimm98y
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Merge pull request #8 from paulomorgado/MJpegTrack
Add MJpegTrack class for RTP MJPEG video handling
2 parents c3539cc + 7511ba5 commit 8943d0c

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‎src/SharpRTSPServer/MJpegTrack.cs‎

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using System;
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using System.Buffers;
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using System.Buffers.Binary;
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using System.Collections.Generic;
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using System.Text;
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namespace SharpRTSPServer
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{
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/// <see href="https://datatracker.ietf.org/doc/html/rfc2435" />
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public class MJpegTrack : TrackBase
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{
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/// <inheritdoc/>
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public override bool IsReady => true;
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/// <inheritdoc/>
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public override int PayloadType { get; set; } = 26; // RTP_PT_JPEG - https://datatracker.ietf.org/doc/html/rfc2435 - Appendix C
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/// <inheritdoc/>
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public override string Codec => "JPEG";
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/// <inheritdoc/>
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public override int ID { get; set; }
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public int Width { get; set; }
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public int Height { get; set; }
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/// <inheritdoc/>
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public override StringBuilder BuildSDP(StringBuilder sdp)
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{
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return sdp
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.Append("m=video 0 RTP/AVP ").Append(PayloadType).AppendLine()
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.Append("a=control:trackID=").Append(ID).AppendLine()
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;
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}
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/// <inheritdoc/>
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public override (List<Memory<byte>>, List<IMemoryOwner<byte>>) CreateRtpPackets(List<byte[]> samples, uint rtpTimestamp)
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{
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if (samples.Count != 1)
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{
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throw new InvalidOperationException("Only 1 sample is supported.");
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}
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var rtpPackets = new List<Memory<byte>>();
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var memoryOwners = new List<IMemoryOwner<byte>>();
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for (int i = 0; i < samples.Count; i++)
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{
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// https://en.wikipedia.org/wiki/JPEG_File_Interchange_Format
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const ushort SoiMarker = 0xFFD8; // SOI - Start of image header
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//const ushort App0Header = 0xFFE0; // Application Segment 0 header
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//const ushort App15Header = 0xFFEF; // Application Segment 15 header
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const ushort Sof0Marker = 0xFFC0; // SOF0 - Start of Frame marker
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const ushort DqtHeader = 0xFFDB; // Define Quantization Table header
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//const ushort SosMarker = 0xFFDA; // SOS - Start of Scan marker
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const ushort EoiMarker = 0xFFD9; // EOI - End of Image marker
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var jpegImage = samples[i].AsSpan();
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var header = BinaryPrimitives.ReadUInt16BigEndian(jpegImage);
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if (header != SoiMarker)
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{
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throw new InvalidOperationException($"JPEG image must start with SOI marker {SoiMarker.ToString("X4")} and {header.ToString("X4")}");
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}
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header = BinaryPrimitives.ReadUInt16BigEndian(jpegImage.Slice(jpegImage.Length - 2));
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if (header != EoiMarker)
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{
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throw new InvalidOperationException($"JPEG image must start with SOI marker {EoiMarker.ToString("X4")} and {header.ToString("X4")}");
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}
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//var reader = jpegImage[2..^2];
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var reader = jpegImage.Slice(2); // keep EOI
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byte type = 1; // https://datatracker.ietf.org/doc/html/rfc2435#section-3.1.3
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byte q = 255; // https://datatracker.ietf.org/doc/html/rfc2435#section-3.1.4, https://datatracker.ietf.org/doc/html/rfc2435#section-4.2
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int nbQuantizationTables = 0;
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var firstQuantizationtable = ReadOnlySpan<byte>.Empty;
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var secondQuantizationtable = ReadOnlySpan<byte>.Empty;
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while (true)
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{
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header = BinaryPrimitives.ReadUInt16BigEndian(reader);
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if (header == Sof0Marker)
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{
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break;
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}
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reader = reader.Slice(2);
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var size = BinaryPrimitives.ReadUInt16BigEndian(reader) - 2; reader = reader.Slice(2);
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switch (header)
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{
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case DqtHeader:
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nbQuantizationTables++;
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if (nbQuantizationTables == 1)
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{
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firstQuantizationtable = reader.Slice(0, size);
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}
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else if (nbQuantizationTables == 2)
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{
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secondQuantizationtable = reader.Slice(0, size);
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}
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else
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{
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throw new InvalidOperationException("Error: More than 2 quantization tables in JPEG image");
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}
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break;
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default:
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break;
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}
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reader = reader.Slice(size);
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}
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// Build a list of 1 or more RTP packets
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// The last packet will have the M bit set to '1'
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var endOfFrame = false;
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var firstFrame = true;
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// -8 for UDP header, -20 for IP header, -16 normal RTP header len. ** LESS RTP EXTENSIONS !!!
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var packetMTU = 1400; // 65535;
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var dataPointer = 0;
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while (reader.Length > 0)
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{
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bool shouldSendQuantizationTables = firstFrame && q > 127;
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firstFrame = false;
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int payloadSize = Math.Min(packetMTU, reader.Length);
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endOfFrame = payloadSize == reader.Length;
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// 12 is header size. then jpeg header, then payload
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var destSize = 12 + 8 + payloadSize;
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var owner = MemoryPool<byte>.Shared.Rent(destSize);
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memoryOwners.Add(owner);
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var rtpPacket = owner.Memory.Slice(0, destSize);
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// RTP Packet Header
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// 0 - Version, P, X, CC, M, PT and Sequence Number
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//32 - Timestamp. H264 uses a 90kHz clock
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//64 - SSRC
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//96 - CSRCs (optional)
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//nn - Extension ID and Length
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//nn - Extension header
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var rtpPacketSpan = rtpPacket.Span;
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rtpPacketSpan.Slice(3, 9).Clear();
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RTPPacketUtil.WriteHeader(
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rtpPacket: rtpPacketSpan,
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rtpVersion: RTPPacketUtil.RTP_VERSION,
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rtpPadding: false,
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rtpExtension: false,
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rtpCsrcCount: 0,
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rtpMarker: endOfFrame,
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rtpPayloadType: PayloadType);
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// sequence number and SSRC are set just before send
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RTPPacketUtil.WriteTS(rtpPacketSpan, rtpTimestamp);
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rtpPacketSpan = rtpPacketSpan.Slice(12);
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// For JPEG we need https://www.rfc-editor.org/rfc/rfc2435
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BinaryPrimitives.WriteInt32BigEndian(rtpPacketSpan, dataPointer & 0x00FFFFFF);
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rtpPacketSpan = rtpPacketSpan.Slice(4);
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// Write JPEG Header - https://datatracker.ietf.org/doc/html/rfc2435#section-3.1
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rtpPacketSpan[0] = type;
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rtpPacketSpan[1] = q;
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rtpPacketSpan[2] = (byte)(Width / 8);
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rtpPacketSpan[3] = (byte)(Height / 8);
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rtpPacketSpan = rtpPacketSpan.Slice(4);
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// write quantization tables
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if (shouldSendQuantizationTables)
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{
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// Write Restart Marker header - https://datatracker.ietf.org/doc/html/rfc2435#section-3.1.7
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// Not present for type 1
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// Write Quantization Table header https://datatracker.ietf.org/doc/html/rfc2435#section-3.1.8
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if (nbQuantizationTables == 1)
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{
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// MBZ
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rtpPacketSpan[0] = (byte)(firstQuantizationtable[0] & 0xf);
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// Precision
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rtpPacketSpan[1] = (byte)(firstQuantizationtable[0] >> 4);
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// Length
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var qtSize = firstQuantizationtable.Length - 1;
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BinaryPrimitives.WriteInt16BigEndian(rtpPacketSpan.Slice(2), (short)(qtSize));
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// Quantization Table Data
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firstQuantizationtable.Slice(1).CopyTo(rtpPacketSpan.Slice(4));
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qtSize += 4;
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rtpPacketSpan = rtpPacketSpan.Slice(qtSize);
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payloadSize -= qtSize;
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}
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else // nbQuantizationTables == 2
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{
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// MBZ
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rtpPacketSpan[0] = 0;
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// Precision
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rtpPacketSpan[1] = (byte)(firstQuantizationtable[0] >> 4);
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// Length
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var qtSize = firstQuantizationtable.Length + secondQuantizationtable.Length - 2;
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BinaryPrimitives.WriteInt16BigEndian(rtpPacketSpan.Slice(2), (short)(qtSize));
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// Quantization Table Data
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firstQuantizationtable.Slice(1).CopyTo(rtpPacketSpan.Slice(4));
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secondQuantizationtable.Slice(1).CopyTo(rtpPacketSpan.Slice(3 + firstQuantizationtable.Length));
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qtSize += 4;
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rtpPacketSpan = rtpPacketSpan.Slice(qtSize);
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payloadSize -= qtSize;
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}
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}
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// Write JPEG Payload
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reader.Slice(0, rtpPacketSpan.Length).CopyTo(rtpPacketSpan);
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reader = reader.Slice(rtpPacketSpan.Length);
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dataPointer += rtpPacketSpan.Length;
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rtpPackets.Add(rtpPacket);
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}
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}
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return (rtpPackets, memoryOwners);
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}
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}
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}

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