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VideoHeader.cs

//
// VideoHeader.cs: Provides information about an MPEG video stream.
//
// Author:
//   Brian Nickel (brian.nickel@gmail.com)
//
// Copyright (C) 2007 Brian Nickel
// 
// This library is free software; you can redistribute it and/or modify
// it  under the terms of the GNU Lesser General Public License version
// 2.1 as published by the Free Software Foundation.
//
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
// USA
//

using System;

namespace TagLib.Mpeg {
      /// <summary>
      ///    This structure implements <see cref="IVideoCodec" /> and provides
      ///    information about an MPEG video stream.
      /// </summary>
00031       public struct VideoHeader : IVideoCodec
      {
            #region Private Static Fields
            
            /// <summary>
            ///    Contains frame rate values.
            /// </summary>
00038             private static readonly double[] frame_rates = new double[9] {
                  0, 24000d/1001d, 24, 25, 30000d/1001d, 30, 50,
                  60000d/1001d, 60
            };
            
            #endregion
            
            
            
            #region Private Fields
            
            /// <summary>
            ///    Contains the video width.
            /// </summary>
00052             int width;
            
            /// <summary>
            ///    Contains the video height.
            /// </summary>
00057             int height;
            
            /// <summary>
            ///    Contains the index in <see cref="frame_rates" /> of the
            ///    video frame rate.
            /// </summary>
00063             int frame_rate_index;
            
            /// <summary>
            ///    Contains the video bitrate.
            /// </summary>
00068             int bitrate;
            
            #endregion
            
            
            
            #region Constructors
            
            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="VideoHeader" /> by reading it from a specified
            ///    location in a specified file.
            /// </summary>
            /// <param name="file">
            ///    A <see cref="TagLib.File" /> object to read from.
            /// </param>
            /// <param name="position">
            ///    A <see cref="long" /> value indicating the position in
            ///    <paramref name="file" /> at which the header begins.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="file" /> is <see langword="null" />.
            /// </exception>
            /// <exception cref="CorruptFileException">
            ///    Insufficient data could be read for the header.
            /// </exception>
00094             public VideoHeader (TagLib.File file, long position)
            {
                  if (file == null)
                        throw new ArgumentNullException ("file");
                  
                  file.Seek (position);
                  ByteVector data = file.ReadBlock (7);
                  
                  if (data.Count < 7)
                        throw new CorruptFileException (
                              "Insufficient data in header.");
                  
                  width = data.Mid (0, 2).ToUShort () >> 4;
                  height = data.Mid (1, 2).ToUShort () & 0x0FFF;
                  frame_rate_index = data [3] & 0x0F;
                  bitrate = (int) ((data.Mid (4, 3).ToUInt () >> 6) &
                        0x3FFFF);
            }
            
            #endregion
            
            
            
            #region Public Properties
            
            /// <summary>
            ///    Gets the duration of the media represented by the current
            ///    instance.
            /// </summary>
            /// <value>
            ///    Always <see cref="TimeSpan.Zero" />.
            /// </value>
00126             public TimeSpan Duration {
                  get {return TimeSpan.Zero;}
            }
            
            /// <summary>
            ///    Gets the types of media represented by the current
            ///    instance.
            /// </summary>
            /// <value>
            ///    Always <see cref="MediaTypes.Video" />.
            /// </value>
00137             public MediaTypes MediaTypes {
                  get {return MediaTypes.Video;}
            }
            
            /// <summary>
            ///    Gets a text description of the media represented by the
            ///    current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="string" /> object containing a description
            ///    of the media represented by the current instance.
            /// </value>
00149             public string Description {
                  get {return "MPEG Video";}
            }
            
            /// <summary>
            ///    Gets the width of the video represented by the current
            ///    instance.
            /// </summary>
            /// <value>
            ///    A <see cref="int" /> value containing the width of the
            ///    video represented by the current instance.
            /// </value>
00161             public int VideoWidth {
                  get {return width;}
            }
            
            /// <summary>
            ///    Gets the height of the video represented by the current
            ///    instance.
            /// </summary>
            /// <value>
            ///    A <see cref="int" /> value containing the height of the
            ///    video represented by the current instance.
            /// </value>
00173             public int VideoHeight {
                  get {return height;}
            }
            
            /// <summary>
            ///    Gets the frame rate of the video represented by the
            ///    current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="double" /> value containing the frame rate
            ///    of the video represented by the current instance.
            /// </value>
00185             public double VideoFrameRate {
                  get {
                        return frame_rate_index < 9 ? 
                              frame_rates [frame_rate_index] : 0;
                  }
            }
            
            /// <summary>
            ///    Gets the bitrate of the video represented by the current
            ///    instance.
            /// </summary>
            /// <value>
            ///    A <see cref="int" /> value containing a bitrate of the
            ///    video represented by the current instance.
            /// </value>
00200             public int VideoBitrate {
                  get {return bitrate;}
            }
            
            #endregion
      }
}

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