mediafield.cs

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using SDP;
using System.Collections.Generic;

/// <summary>
/// A Media represents an m= field contained within a MediaDescription. The Media identifies 
/// information about the format(s) of the media associated with the MediaDescription. 
/// 
/// The Media field includes:
///     a mediaType (e.g. audio, video, etc.)
///     a port number (or set of ports)
///     a protocol to be used (e.g. RTP/AVP)
///     a set of media formats which correspond to Attributes associated with the media description.
/// Here is an example:
/// 
/// m=audio 60000 RTP/AVP 0
/// a=rtpmap:0 PCMU/8000
/// 
/// This example identifies that the client can receive audio on port 60000 in format 0 which 
/// corresponds to PCMU/8000.
/// </summary>
public class MediaField : Field
{
    private string mediaType;
    /// <summary>
    /// Gets the primary MIME type. See <see cref="MediaTypes"/>
    /// </summary>
    public string MediaType
    {
        get { return this.mediaType; }
    }

    private PortRange mediaPort;
    /// <summary>
    /// Gets the port range this media uses.
    /// </summary>
    public PortRange MediaPort
    {
        get { return this.mediaPort; }
    }

    private string protocol;
    /// <summary>
    /// Gets the network transport protocol for this media. Preliminarily defined
    /// protocols are "RTP/AVP" and "udp".
    /// </summary>
    public string Protocol
    {
        get { return this.protocol; }
    }

    private List<string> mediaFormats;
    /// <summary>
    /// Gets a list of media formats. From RFC 2327:
    /// 
    /// The fourth and subsequent sub-fields are media formats.  For audio
    /// and video, these will normally be a media payload type as defined
    /// in the RTP Audio/Video Profile.
    /// 
    /// When a list of payload formats is given, this implies that all of
    /// these formats may be used in the session, but the first of these
    /// formats is the default format for the session.
    /// 
    /// For media whose transport protocol is not RTP or UDP the format
    /// field is protocol specific.  Such formats should be defined in an
    /// additional specification document.
    /// </summary>
    public List<string> MediaFormats
    {
        get { return this.mediaFormats; }
    }

    /// <summary>
    /// Creates a new MediaField.
    /// </summary>
    /// <param name="value">The value portion of the field.</param>
    public MediaField(string value)
        : base("m=" + value)
    {
        string val = base.value;
        string[] parts = val.Split(' ');
        this.mediaType = parts[0];

        string[] port = parts[1].Split('/');
        if (port.Length > 1)
            this.mediaPort = new PortRange(ushort.Parse(port[0]), ushort.Parse(port[1]));
        else this.mediaPort = new PortRange(ushort.Parse(port[0]));

        this.protocol = parts[2];

        parts.CopyTo(parts, 3);
        this.mediaFormats = new List<string>(parts);
    }

    /// <summary>
    /// Creates a new MediaField.
    /// </summary>
    /// <param name="mediaType">The type of media.</param>
    /// <param name="protocol">The transport protocol.</param>
    /// <param name="ports">The port range this media operates on.</param>
    /// <param name="formats">The formats this media will use.</param>
    public MediaField(string mediaType, string protocol, PortRange ports, params string[] formats)
        : this(helpConsolidate(mediaType, protocol, ports, formats)) { }

    private static string helpConsolidate(string mediaType, string protocol, PortRange ports, string[] formats)
    {
        string s = mediaType + " " + ports.ToString() + " " + protocol;
        foreach (string ss in formats)
            s = s + " " + ss;
        return s;
    }
}