Set metadata to mp4

Question

I encode video with help of MediaCodec and MediaMuxer. As result I have mp4 video file. How can I set metadata (creating time) to this mp4 file? MediaMetadataRetriever can only read metadata, but not change. I don't want to use ffmpeg. I tried mp4parser library (this class), but it doesn't work for me.

Answer 1

Setting metadata in MP4 file is not a clear task because there is no generally supported specification, but most video players support Apple specs.

More info here, here, and here.

Here is the code which sets title and creation date in MP4 metadata (based on MetaDataInsert.java sample):

import com.coremedia.iso.IsoFile;
import com.coremedia.iso.boxes.*;
import com.coremedia.iso.boxes.apple.AppleItemListBox;
import com.googlecode.mp4parser.boxes.apple.AppleNameBox;
import com.googlecode.mp4parser.boxes.apple.AppleRecordingYear2Box;
import com.googlecode.mp4parser.util.Path;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.util.List;

public class Mp4MetadataWriter {

    public FileChannel splitFileAndInsert(File f, long pos, long length) throws IOException {
        FileChannel read = new RandomAccessFile(f, "r").getChannel();
        File tmp = File.createTempFile("ChangeMetaData", "splitFileAndInsert");
        FileChannel tmpWrite = new RandomAccessFile(tmp, "rw").getChannel();
        read.position(pos);
        tmpWrite.transferFrom(read, 0, read.size() - pos);
        read.close();
        FileChannel write = new RandomAccessFile(f, "rw").getChannel();
        write.position(pos + length);
        tmpWrite.position(0);
        long transferred = 0;
        while ((transferred += tmpWrite.transferTo(0, tmpWrite.size() - transferred, write)) != tmpWrite.size()) {
            System.out.println(transferred);
        }
        System.out.println(transferred);
        tmpWrite.close();
        tmp.delete();
        return write;
    }


    private boolean needsOffsetCorrection(IsoFile isoFile) {
        if (Path.getPath(isoFile, "moov[0]/mvex[0]") != null) {
            // Fragmented files don't need a correction
            return false;
        } else {
            // no correction needed if mdat is before moov as insert into moov want change the offsets of mdat
            for (Box box : isoFile.getBoxes()) {
                if ("moov".equals(box.getType())) {
                    return true;
                }
                if ("mdat".equals(box.getType())) {
                    return false;
                }
            }
            throw new RuntimeException("I need moov or mdat. Otherwise all this doesn't make sense");
        }
    }

    public void writeMetadata(String videoFilePath, String theTitle, String theDate) throws IOException {

        File videoFile = new File(videoFilePath);
        if (!videoFile.exists()) {
            throw new FileNotFoundException("File " + videoFilePath + " not exists");
        }

        if (!videoFile.canWrite()) {
            throw new IllegalStateException("No write permissions to file " + videoFilePath);
        }
        IsoFile isoFile = new IsoFile(videoFilePath);

        MovieBox moov = isoFile.getBoxes(MovieBox.class).get(0);
        FreeBox freeBox = findFreeBox(moov);

        boolean correctOffset = needsOffsetCorrection(isoFile);
        long sizeBefore = moov.getSize();
        long offset = 0;
        for (Box box : isoFile.getBoxes()) {
            if ("moov".equals(box.getType())) {
                break;
            }
            offset += box.getSize();
        }

        // Create structure or just navigate to Apple List Box.
        UserDataBox userDataBox;
        if ((userDataBox = Path.getPath(moov, "udta")) == null) {
            userDataBox = new UserDataBox();
            moov.addBox(userDataBox);
        }
        MetaBox metaBox;
        if ((metaBox = Path.getPath(userDataBox, "meta")) == null) {
            metaBox = new MetaBox();
            HandlerBox hdlr;
            hdlr = new HandlerBox();
            hdlr.setHandlerType("mdir");
            metaBox.addBox(hdlr);
            userDataBox.addBox(metaBox);
        }
        AppleItemListBox ilst;
        if ((ilst = Path.getPath(metaBox, "ilst")) == null) {
            ilst = new AppleItemListBox();
            metaBox.addBox(ilst);

        }
        if (freeBox == null) {
            freeBox = new FreeBox(128 * 1024);
            metaBox.addBox(freeBox);
        }

        // Got Apple List Box

        AppleNameBox nam;
        if ((nam = Path.getPath(ilst, AppleNameBox.TYPE)) == null) {
            nam = new AppleNameBox();
        }
        nam.setDataCountry(0);
        nam.setDataLanguage(0);
        nam.setValue(theTitle);
        ilst.addBox(nam);

        AppleRecordingYear2Box day;
        if ((day = Path.getPath(ilst, "©day")) == null) {
            day = new AppleRecordingYear2Box();
        }
        day.setDataCountry(0);
        day.setDataLanguage(0);
        day.setValue(theDate);
        ilst.addBox(day);

        long sizeAfter = moov.getSize();
        long diff = sizeAfter - sizeBefore;
        // This is the difference of before/after

        // can we compensate by resizing a Free Box we have found?
        if (freeBox.getData().limit() > diff) {
            // either shrink or grow!
            freeBox.setData(ByteBuffer.allocate((int) (freeBox.getData().limit() - diff)));
            sizeAfter = moov.getSize();
            diff = sizeAfter - sizeBefore;
        }
        if (correctOffset && diff != 0) {
            correctChunkOffsets(moov, diff);
        }
        BetterByteArrayOutputStream baos = new BetterByteArrayOutputStream();
        moov.getBox(Channels.newChannel(baos));
        isoFile.close();
        FileChannel fc;
        if (diff != 0) {
            // this is not good: We have to insert bytes in the middle of the file
            // and this costs time as it requires re-writing most of the file's data
            fc = splitFileAndInsert(videoFile, offset, sizeAfter - sizeBefore);
        } else {
            // simple overwrite of something with the file
            fc = new RandomAccessFile(videoFile, "rw").getChannel();
        }
        fc.position(offset);
        fc.write(ByteBuffer.wrap(baos.getBuffer(), 0, baos.size()));
        fc.close();
    }

    FreeBox findFreeBox(Container c) {
        for (Box box : c.getBoxes()) {
            System.err.println(box.getType());
            if (box instanceof FreeBox) {
                return (FreeBox) box;
            }
            if (box instanceof Container) {
                FreeBox freeBox = findFreeBox((Container) box);
                if (freeBox != null) {
                    return freeBox;
                }
            }
        }
        return null;
    }

    private void correctChunkOffsets(MovieBox movieBox, long correction) {
        List<ChunkOffsetBox> chunkOffsetBoxes = Path.getPaths((Box) movieBox, "trak/mdia[0]/minf[0]/stbl[0]/stco[0]");
        if (chunkOffsetBoxes.isEmpty()) {
            chunkOffsetBoxes = Path.getPaths((Box) movieBox, "trak/mdia[0]/minf[0]/stbl[0]/st64[0]");
        }
        for (ChunkOffsetBox chunkOffsetBox : chunkOffsetBoxes) {
            long[] cOffsets = chunkOffsetBox.getChunkOffsets();
            for (int i = 0; i < cOffsets.length; i++) {
                cOffsets[i] += correction;
            }
        }
    }

    private static class BetterByteArrayOutputStream extends ByteArrayOutputStream {
        byte[] getBuffer() {
            return buf;
        }
    }

}

Usage:

new Mp4MetadataWriter().writeMetadata("/home/user/downloads/1.mp4", "Yet another video title", "2020");

Result: