// --- children ---
protected void readChildren(MP4InputStream inStream)
{
while ((size - (inStream.getOffset() - start)) > 0)
{
Descriptor desc = createDescriptor(inStream);
children.Add(desc);
}
}
public void readChildren(MP4InputStream inStream)
{
while (inStream.getOffset() < (offset + size))
{
var box = BoxFactory.parseBox(this, inStream);
children.Add(box);
}
}
public static Descriptor createDescriptor(MP4InputStream inStream)
{
//read tag and size
int type = inStream.read();
int read = 1;
int size = 0;
int b = 0;
do
{
b = inStream.read();
size <<= 7;
size |= b & 0x7f;
read++;
}while ((b & 0x80) == 0x80);
//create descriptor
Descriptor desc = forTag(type);
desc.type = type;
desc.size = size;
desc.start = inStream.getOffset();
//decode
desc.decode(inStream);
//skip remaining bytes
long remaining = size - (inStream.getOffset() - desc.start);
if (remaining > 0)
{
Logger.LogBoxes(string.Format("Descriptor: bytes left: {0:N0}, offset: {1:N0}", remaining, inStream.getOffset()));
inStream.skipBytes(remaining);
}
desc.size += read; //include type and size fields
return(desc);
}
/// <summary>
/// Reads the next frame from this track. If it contains no more frames to read, null is returned.
/// </summary>
/// <returns>the next frame or null if there are no more frames to read</returns>
public Frame readNextFrame()
{
Frame frame = null;
if (hasMoreFrames())
{
frame = frames[currentFrame];
long diff = frame.getOffset() - inStream.getOffset();
if (diff > 0)
{
inStream.skipBytes(diff);
}
else if (diff < 0)
{
if (inStream.hasRandomAccess())
{
inStream.seek(frame.getOffset());
}
else
{
Logger.LogServe(string.Format("MP4 API: readNextFrame failed: frame {0:N0} already skipped, offset:{1:N0}, stream:{2:N0}", currentFrame, frame.getOffset(), inStream.getOffset()));
throw new IOException("frame already skipped and no random access");
}
}
var b = new byte[(int)frame.getSize()];
try
{
inStream.read(b, 0, b.Length);
}
catch (Exception)
{
Logger.LogServe(string.Format("MP4 API: readNextFrame failed: tried to read {0:N0} bytes at {1:N0}", frame.getSize(), inStream.getOffset()));
throw;
}
frame.setData(b);
currentFrame++;
}
return(frame);
}
public static IBox parseBox(IBox parent, MP4InputStream inStream)
{
long offset = inStream.getOffset();
long size = inStream.readBytes(4);
var type = (BoxType)(uint)inStream.readBytes(4);
if (size == 1)
{
size = inStream.readBytes(8);
}
if (type == BoxType.EXTENDED_TYPE)
{
inStream.skipBytes(16);
}
if (type == 0)
{
return(new UnknownBox());
}
// --- error protection ---
if (parent != null)
{
long parentLeft = (parent.getOffset() + parent.getSize()) - offset;
if (size > parentLeft)
{
throw new Exception("error while decoding box '" + type + "' ('" + typeToString(type) + "') at offset " + offset.ToString("N0") + ": box too large for parent");
}
}
Logger.LogBoxes("[" + offset.ToString("N0") + "] " + GetBoxPath(type, parent));
var box = forType(type, inStream.getOffset());
box.setParams(parent, size, type, offset);
box.decode(inStream);
// --- if box doesn't contain data it only contains children ---
if (box.GetType() == typeof(BoxImpl) || box.GetType() == typeof(FullBox))
{
box.readChildren(inStream);
}
// --- check bytes left ---
long left = (box.getOffset() + box.getSize()) - inStream.getOffset();
if (left > 0)
{
if (!(box is MediaDataBox) && !(box is UnknownBox) && !(box is FreeSpaceBox))
{
Logger.LogInfo(string.Format("bytes left after reading box {0}: left: {1}, offset: {2}", typeToString(type), left, inStream.getOffset()));
}
// --- skip left Data ---
inStream.skipBytes(left);
}
else if (left < 0)
{
Logger.LogServe(string.Format("box {0} overread: {1} bytes, offset: {2}", typeToString(type), -left, inStream.getOffset()));
}
return(box);
}
protected long getLeft(MP4InputStream inStream)
{
return((offset + size) - inStream.getOffset());
}