/// <summary>
/// Creates a PSSH (Protection System Specific Header) box suitable for embedding into a media
/// file that follows the ISO Base Media File Format specification.
/// </summary>
public static byte[] CreatePsshBox(this HelpersContainerClasses.Media container, Guid systemId, byte[] data)
{
Helpers.Argument.ValidateIsNotNull(data, nameof(data));
// Size (32) BE
// Type (32)
// Version (8)
// Flags (24)
// SystemID (16*8) BE
// DataSize (32) BE
// Data (DataSize*8)
using (var buffer = new MemoryStream())
{
using (var writer = new MultiEndianBinaryWriter(buffer, ByteOrder.BigEndian))
{
writer.Write(4 + 4 + 1 + 3 + 16 + 4 + data.Length);
writer.Write(new[] { 'p', 's', 's', 'h' });
writer.Write(0); // 0 flags, 0 version.
writer.Write(systemId.ToBigEndianByteArray());
writer.Write(data.Length);
writer.Write(data);
}
return(buffer.ToArray());
}
}
/// <summary>
/// Calculates the required crop data in order to crop a picture into the desired aspect ratio.
/// </summary>
public static CropResult Crop(this HelpersContainerClasses.Media container, int width, int height, double targetAspectRatio)
{
Helpers.Argument.ValidateRange(width, nameof(width), 1);
Helpers.Argument.ValidateRange(height, nameof(height), 1);
Helpers.Argument.ValidateRange(targetAspectRatio, nameof(targetAspectRatio), double.Epsilon);
var inputAspectRatio = width * 1.0 / height;
int outputHeight;
int outputWidth;
// 1) Decide which way to adjust - does the input need to become wider or narrower.
// 2) Decrease the appropriate dimension of the input, giving the first output dimension.
// 3) Calculate the other output dimension based on the target aspect ratio.
// 4) Center the crop rectangle in the input.
if (targetAspectRatio > inputAspectRatio)
{
// We need to make it wider - crop top and bottom.
// We round the results to avoid needless cropping but avoid going out of bounds at all times.
outputHeight = (int)Math.Min(height, Math.Round(width / targetAspectRatio, MidpointRounding.AwayFromZero));
outputWidth = (int)Math.Min(width, Math.Round(outputHeight * targetAspectRatio, MidpointRounding.AwayFromZero));
}
else
{
// We need to make it narrower - crop left and right.
// We round the results to avoid needless cropping but avoid going out of bounds at all times.
outputWidth = (int)Math.Min(width, Math.Round(height * targetAspectRatio, MidpointRounding.AwayFromZero));
outputHeight = (int)Math.Min(height, Math.Round(outputWidth / targetAspectRatio, MidpointRounding.AwayFromZero));
}
return(new CropResult
{
Width = outputWidth,
Height = outputHeight,
XOffset = (width - outputWidth) / 2,
YOffset = (height - outputHeight) / 2
});
}
/// <summary>
/// Extracts the key IDs from a protected media file. The contents of the input stream can be any supported
/// type of presentation manifest or container file that contains key IDs.
/// </summary>
/// <remarks>
/// Currently supports Smooth Streaming and DASH manifests as input.
/// </remarks>
/// <returns>
/// The set of key IDs found or an empty set if the input was valid but contained no key IDs.
/// No duplicates will be returned.
/// </returns>
public static ICollection <Guid> GetKeyIds(this HelpersContainerClasses.Media container, Stream stream)
{
Helpers.Argument.ValidateIsNotNull(stream, nameof(stream));
var document = XDocument.Load(stream);
// If we are dealing with a Smooth Streaming manifest, we will find the protection data here.
var playReadyProtectionHeaders = document.Root.Element("Protection")?.Elements("ProtectionHeader")?.Where(ph =>
{
var systemIdAttribute = ph.Attribute("SystemID");
if (systemIdAttribute == null)
{
return(false);
}
var systemId = Guid.Parse(systemIdAttribute.Value);
return(systemId == PlayReadyConstants.SystemId);
}).ToArray();
if (playReadyProtectionHeaders != null)
{
var keyIds = new List <Guid>();
foreach (var header in playReadyProtectionHeaders)
{
var playReadyHeader = Convert.FromBase64String(header.Value);
var headerKeyId = Helpers.PlayReady.GetKeyIdFromPlayReadyHeader(playReadyHeader);
keyIds.Add(headerKeyId);
}
return(keyIds.Distinct().ToArray());
}
// If we are dealing with a DASH manifest, we will find the protection data here.
// Note that this assumes the manifest is GPMF v6 compatible (protection info under AdaptationSet).
var adaptationSets = document.Root
.Elements(DashConstants.PeriodName)
.Elements(DashConstants.AdaptationSetName)
.ToArray();
if (adaptationSets.Length != 0)
{
var keyIds = new List <Guid>();
foreach (var adaptationSet in adaptationSets)
{
// DASH-IF IOP v3 7.5.2 says that ContentProtection must be defined directly under the adaptation set.
// DASH allows it to also be elsewhere but we do not support those scenarios.
var contentProtections = adaptationSet
.Elements(DashConstants.ContentProtectionName)
.ToArray();
// Not a protected adaptation set. That's fine, ignore it.
if (contentProtections.Length == 0)
{
continue;
}
var mp4ContentProtections = contentProtections.Where(cp => cp.Attribute("schemeIdUri")?.Value == "urn:mpeg:dash:mp4protection:2011").ToArray();
if (mp4ContentProtections.Length == 0)
{
throw new InvalidDataException("The DASH manifest has protected content but is missing the required mp4protection signaling.");
}
if (mp4ContentProtections.Length != 1)
{
throw new InvalidDataException("Multiple mp4protection signaling elements detected for a single adaptation set.");
}
var defaultKidAttribute = mp4ContentProtections.Single().Attribute(DashConstants.DefaultKidAttributeName);
if (defaultKidAttribute == null)
{
throw new InvalidDataException("There is no cenc:default_KID attribute on the mp4protection signaling element.");
}
Guid kid;
if (!Guid.TryParse(defaultKidAttribute.Value, out kid))
{
throw new InvalidDataException("The value of the cenc:default_KID attribute is not a valid GUID.");
}
keyIds.Add(kid);
}
return(keyIds.Distinct().ToArray());
}
// No protection information found.
return(new Guid[0]);
}
