// Appends to `samples'.
// Returns nextStartTime.
private static ulong ParseFragment(Fragment fragment, IList<MediaSample> samples, MediaStreamType type,
ulong chunkStartTime)
{
// A fragment is a ``chunk'' (with a corresponding <c d=....> in its duration) in the ISM manifest file.
TrackFragmentBox traf = fragment.moof.traf;
if (traf.tfxd != null) {
chunkStartTime = traf.tfxd.FragmentAbsoluteTime;
}
ulong nextStartTime = 0uL;
if (traf.tfrf != null && traf.tfrf.Array.Length > 0u) {
nextStartTime = traf.tfrf.Array[0].FragmentAbsoluteTime;
}
long sampleOffset = fragment.mdat.Start;
uint defaultSampleSize = traf.tfhd.default_sample_size;
uint sampleSize = defaultSampleSize;
uint defaultSampleDuration = traf.tfhd.default_sample_duration;
uint duration = defaultSampleDuration;
ulong totalDuration = 0;
uint sampleCount = traf.trun.sample_count;
TrackRunBox.Element[] array = defaultSampleSize == 0u || defaultSampleDuration == 0u ? traf.trun.array : null;
for (uint i = 0; i < sampleCount; ++i) {
if (defaultSampleSize == 0u) {
sampleSize = array[i].sample_size;
}
if (defaultSampleDuration == 0u) {
duration = array[i].sample_duration;
}
// We add a few dozen MediaSample entries for a chunk.
samples.Add(new MediaSample(sampleOffset, (int)sampleSize, chunkStartTime,
/*isKeyFrame:*/i == 0 || type == MediaStreamType.Audio));
chunkStartTime += (ulong)duration;
totalDuration += (ulong)duration;
sampleOffset += sampleSize;
}
return nextStartTime != 0uL ? nextStartTime : chunkStartTime;
}
// Modifies track in place, and appends to mediaSamples.
// Returns null on network failure or empty file, otherwise it returns a non-empty array.
// The chunk file contents are returned, and are not saved to disk.
internal static byte[] DownloadChunk(TrackInfo trackInfo, IList<MediaSample> mediaSamples, ulong chunkStartTime,
string manifestParentPath, bool isLive, out ulong nextStartTime)
{
nextStartTime = 0; // Set even if null is returned.
string chunkUrl = trackInfo.Stream.GetChunkUrl(trackInfo.Bitrate, chunkStartTime);
// TODO: Move TrackInfo away from Track, keep only fields necessary here, excluding ChunkList.
byte[] downloadedBytes; // Will be set below.
if (manifestParentPath != null) { // It was a local manifest, so read the chunk from a local file.
if (!chunkUrl.StartsWith(LOCAL_URL_PREFIX)) {
throw new Exception("ASSERT: Missing local URL prefix.");
}
// Example chunk URL: "http://local/QualityLevels(900000)/Fragments(video=0)".
// TODO: Maybe this needs some further unescaping of %5A etc. (can be tested locally).
string chunkDownloadedPath = manifestParentPath + Path.DirectorySeparatorChar +
chunkUrl.Substring(LOCAL_URL_PREFIX.Length).Replace('/', Path.DirectorySeparatorChar);
using (FileStream fileStream = new FileStream(chunkDownloadedPath, FileMode.Open)) {
downloadedBytes = ReadFileStream(fileStream);
}
if (downloadedBytes.Length == 0) {
Console.WriteLine();
Console.WriteLine("Local chunk file empty: " + chunkDownloadedPath);
return null;
}
} else { // Download from the web.
WebClient webClient = new WebClient();
try {
// TODO: What's the timeout on this?
downloadedBytes = webClient.DownloadData(chunkUrl);
} catch (WebException) {
Thread.Sleep(isLive ? 4000 : 2000);
try {
downloadedBytes = webClient.DownloadData(chunkUrl);
} catch (WebException) {
Thread.Sleep(isLive ? 6000 : 3000);
try {
downloadedBytes = webClient.DownloadData(chunkUrl);
} catch (WebException) {
// It's an acceptable behavior to stop downloading live streams after 10 seconds.
// If it's really live, there should be a new chunk update available every 10 seconds.
Console.WriteLine();
Console.WriteLine("Error downloading chunk " + chunkUrl);
return null;
}
}
}
}
if (downloadedBytes.Length == 0) {
Console.WriteLine();
Console.WriteLine("Chunk empty: " + chunkUrl);
return null;
}
Fragment fragment = new Fragment(downloadedBytes, 0, downloadedBytes.Length);
// This appends to mediaSamples.
nextStartTime = ParseFragment(fragment, mediaSamples, trackInfo.Stream.Type, chunkStartTime);
if (nextStartTime <= chunkStartTime) {
throw new Exception("Found empty chunk.");
}
return downloadedBytes;
}
