How to find the address where width and height are stored inside an mp4 file? - data-structures

Question

I need to find the addresses where the width and height are stored, but the IUT version of the standard don't give a clear definition of the file format.
What I found so far... :
Both values are stored in "a QuickTime float". I couldn't find the format, but it seems it use two 16-bits integer: a signed one followed by an unsigned one.
Unlike many file format, there are no fixed position, so it is file specific. It depend on the TrackHeaderBox address.
What I desperatly need :
A clear canonical answer describing the places to find only those kind of information. I don't want answers only referring to third party libraries (unless they are written in proper JavaScript). Some pseudo C like structures can help.

Answer 1

There is no fixed position. You need to parse into the file. Please check this Java example.
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.List;
public class GetHeight {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream(new File(args[0]));
GetHeight ps = new GetHeight();
ps.find(fis);
}
byte[] lastTkhd;
private void find(InputStream fis) throws IOException {
while (fis.available() > 0) {
byte[] header = new byte[8];
fis.read(header);
long size = readUint32(header, 0);
String type = new String(header, 4, 4, "ISO-8859-1");
if (containers.contains(type)) {
find(fis);
} else {
if (type.equals("tkhd")) {
lastTkhd = new byte[(int) (size - 8)];
fis.read(lastTkhd);
} else {
if (type.equals("hdlr")) {
byte[] hdlr = new byte[(int) (size - 8)];
fis.read(hdlr);
if (hdlr[8] == 0x76 && hdlr[9] == 0x69 && hdlr[10] == 0x64 && hdlr[11] == 0x65) {
System.out.println("Video Track Header identified");
System.out.println("width: " + readFixedPoint1616(lastTkhd, lastTkhd.length - 8));
System.out.println("height: " + readFixedPoint1616(lastTkhd, lastTkhd.length - 4));
System.exit(1);
}
} else {
fis.skip(size - 8);
}
}
}
}
}
public static long readUint32(byte[] b, int s) {
long result = 0;
result |= ((b[s + 0] << 24) & 0xFF000000);
result |= ((b[s + 1] << 16) & 0xFF0000);
result |= ((b[s + 2] << 8) & 0xFF00);
result |= ((b[s + 3]) & 0xFF);
return result;
}
public static double readFixedPoint1616(byte[] b, int s) {
return ((double) readUint32(b, s)) / 65536;
}
List<String> containers = Arrays.asList(
"moov",
"mdia",
"trak"
);
}