PrintStructure example bug about mp4parser

[sannies]

The print structure thingy might or might not work correctly. The trak box
should be on the same level as mvhd. Please check the isoviewer project to
check your mp4s!
Am 03.02.2015 04:45 schrieb "MattStillerman" [email protected]:

The class PrintStructure in package com.google.code.mp4parser.example
seems to have a bug.

The program is supposed to print an indented list of the boxes in the
stream. For each box that is a container, it is supposed to parse the
contents, and print an indented list of boxes inside. You would expect that
the size of a container would correspond to the sum of the sizes of its
"top level" constituents, plus 8 bytes. Here is the beginning of the output
from the program, exhibiting the error:

ftyp@0 size: 24
mdat@24 size: 6930099
moov@6930123 size: 3765
mvhd@13860262 size: 108
udta@13860370 size: 38
©xyz@20790625 size: 30
trak@20790655 size: 2164
tkhd@27720948 size: 92
mdia@27721040 size: 2064
mdhd@34651433 size: 32

This output seems to indicate that the udta box of size 38 contains a ©xyz
box of size 30 and a trak box of size 2164 -- which is impossible.

The error is that the print method, when applied to the contents of a box,
starts with a FileChannel that is positioned at the beginning of the box
data, and it runs to the end of the channel. It should stop when it
reaches the end of the box!

—
Reply to this email directly or view it on GitHub
#47.

[MattStillerman]

Thanks very much! I'll try out the isoviewer.

Here is a fixed version of the class, followed by its output. The trak box is now at the same level as mvhd.

Matt

package com.google.code.mp4parser.example;

import com.coremedia.iso.IsoTypeReader;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;

import com.googlecode.mp4parser.DataSource;

import java.nio.channels.FileChannel;
import java.util.Arrays;
import java.util.List;

/**
 * Created by IntelliJ IDEA.
 * User: sannies
 * Date: 8/5/11
 * Time: 2:03 PM
 * To change this template use File | Settings | File Templates.
 */
public class PrintStructureFixed {
    public static void main(String[] args) throws IOException {
        System.out.println("PWD: " + System.getProperty("user.dir"));
        System.out.println("Input: " + args[0]);
        FileInputStream fis = new FileInputStream(new File(args[0]));
        System.out.println("input size: " + fis.getChannel().size());

        PrintStructureFixed ps = new PrintStructureFixed();
        ps.print(fis.getChannel(), 0, 0, 0);
    }


    /** Parses the FileChannel, in the range [start, end) and prints the elements found
     * 
     * Elements are printed, indented by "level" number of spaces.  If an element is
     * a container, then its contents will be, recursively, printed, with a greater
     * indentation.
     * 
     * @param fc
     * @param level
     * @param start
     * @param end
     * @throws IOException
     */
    private void print(FileChannel fc, int level, long start, long end) throws IOException {
        fc.position(start);
        if(end <= 0) {
            end = start + fc.size();
            System.out.println("Setting END to " + end);
        }
        while (end - fc.position() > 8) {
            long begin = fc.position();
            ByteBuffer bb = ByteBuffer.allocate(8);
            fc.read(bb);
            bb.rewind();
            long size = IsoTypeReader.readUInt32(bb);
            String type = IsoTypeReader.read4cc(bb);
            long fin = begin + size;
            // indent by the required number of spaces
            for (int i = 0; i < level; i++) {
                System.out.print(" ");
            }

            System.out.println(type + "@" + (begin) + " size: " + size);
            if (containers.contains(type)) {
                print(fc, level + 1, begin + 8, fin);
                if(fc.position() != fin) {
                    System.out.println("End of container contents at " + fc.position());
                    System.out.println("  FIN = " + fin);
                }
            }

            fc.position(fin);

        }
    }

    List<String> containers = Arrays.asList(
            "moov",
            "trak",
            "mdia",
            "minf",
            "udta",
            "stbl"
    );
}

Input: mp4parser-master/examples/src/main/resources/1365070453555.mp4
input size: 6933888
Setting END to 6933888
ftyp@0 size: 24
mdat@24 size: 6930099
moov@6930123 size: 3765
 mvhd@6930131 size: 108
 udta@6930239 size: 38
  ©xyz@6930247 size: 30
 trak@6930277 size: 2164
  tkhd@6930285 size: 92
  mdia@6930377 size: 2064
   mdhd@6930385 size: 32
   hdlr@6930417 size: 44
   minf@6930461 size: 1980
    vmhd@6930469 size: 20
    dinf@6930489 size: 36
    stbl@6930525 size: 1916
     stsd@6930533 size: 152
     stts@6930685 size: 1064
     stss@6931749 size: 36
     stsz@6931785 size: 568
     stsc@6932353 size: 52
     stco@6932405 size: 36
 trak@6932441 size: 1447
  tkhd@6932449 size: 92
  mdia@6932541 size: 1347
   mdhd@6932549 size: 32
   hdlr@6932581 size: 44
   minf@6932625 size: 1263
    smhd@6932633 size: 16
    dinf@6932649 size: 36
    stbl@6932685 size: 1203
     stsd@6932693 size: 91
     stts@6932784 size: 96
     stsz@6932880 size: 920
     stsc@6933800 size: 52
     stco@6933852 size: 36