/// <summary>
/// Downloads a new chunk
/// </summary>
/// <param name="baseUrl">the base url of the file to download</param>
/// <param name="urlGenerator">the class that will generator the url for this chunk</param>
/// <param name="chunk">the chunk we are trying to download</param>
/// <param name="completeCallback">the event handler to call when we are complete</param>
/// <param name="instance">A unique id to group downloads. Can be used to group audio and video downloads separately</param>
public static void Start(
string baseUrl,
IUrlGenerator urlGenerator,
MediaChunk chunk,
EventHandler<DownloadCompleteEventArgs> completeCallback,
Guid instance)
{
Tracer.Assert(chunk.Bitrate > 0, String.Format(CultureInfo.InvariantCulture, "Cannot load chunk {0} with zero bitrate.", chunk.Sid));
Downloader downloader = new Downloader(baseUrl, urlGenerator, chunk, completeCallback, instance);
downloader.StartDownload();
}
/// <summary>
/// Initializes a new instance of the Downloader class
/// </summary>
/// <param name="baseUrl">the base url of the file to download</param>
/// <param name="urlGenerator">the module that generates our url</param>
/// <param name="mediaChunk">the chunk we are trying to download</param>
/// <param name="completeCallback">the event handler to call when we are complete</param>
/// <param name="instance">A unique id to group downloads. Can be used to group audio and video downloads separately</param>
private Downloader(
string baseUrl,
IUrlGenerator urlGenerator,
MediaChunk mediaChunk,
EventHandler<DownloadCompleteEventArgs> completeCallback,
Guid instance)
{
m_instanceId = instance;
m_chunk = mediaChunk;
m_url = urlGenerator.GenerateUrlStringForChunk(baseUrl, mediaChunk.StreamId, mediaChunk.ChunkId, mediaChunk.Bitrate, mediaChunk.StartTime, (long)mediaChunk.Duration);
m_url = m_url.Replace('\\', '/');
// Assumption: ChunkId always start from 0
// Add random URL modifier for the first 2 video chunks to make sure they are not in cache.
// We use the first two chunks to get reliable bandwidth estimates.
if (mediaChunk.ChunkId < PacketPairPacketCount && mediaChunk.MediaType == MediaStreamType.Video)
{
m_url = m_url + "?packetpair=" + DateTime.Now.Ticks;
}
if (mediaChunk.Url != m_url)
{
mediaChunk.Url = m_url;
}
m_downloadCompleteEventHandler = completeCallback;
// Add this download object to our table of objects
lock (sm_allDownloads)
{
if (!sm_allDownloads.ContainsKey(m_instanceId))
{
sm_allDownloads.Add(m_instanceId, new List<Downloader>(4));
}
List<Downloader> allMyDownloads = sm_allDownloads[m_instanceId];
allMyDownloads.Add(this);
}
}
