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ファイルから生の AMR オーディオ フレームを抽出するのに問題があり.3gpます。「 http://android.amberfog.com/?p=181 」というリンクをたどりましたが、「mdat」ボックスタイプの代わりに「moov」を取得しました。「moov」ボックスと「mdat」ボックスの場所がデバイスによって異なることをどこかで読みました。.3gpヘッダーを正しくスキップして生の AMR データを抽出する方法を知っている人はいますか? 以下はコード スニペットです。

public AMRFile convert3GPDataToAmr(String rawAmrFilePath) throws IOException {
        if (_3gpFile == null) {
            return null;
        }

        System.out.println("3GP file length: "+_3gpFile.getRawFile().length());
        //FileInputStream is = new FileInputStream(_3gpFile.getRawFile());
        ByteArrayInputStream bis = new ByteArrayInputStream(FileUtils.readFileToByteArray(_3gpFile.getRawFile()));
        // read FileTypeHeader
        System.out.println("Available1: "+bis.available());
        FileTypeBox ftypHeader = new FileTypeBox(bis);
        System.out.println("Available2: "+bis.available());
        String header = ftypHeader.getHeaderAsString();
        if(!FileTypeBox.HEADER_TYPE.equalsIgnoreCase(header)){
            throw new IOException("File is not 3GP. ftyp header missing.");
        }
        // You can check if it is correct here
        // read MediaDataHeader
        MediaDataBox mdatHeader = new MediaDataBox(bis);
        System.out.println("Available3: "+bis.available());
        header = mdatHeader.getHeaderAsString();
        if(!MediaDataBox.HEADER_TYPE.equalsIgnoreCase(header)){
            //here is THE PROBLEM!!!!! - header is "moov" instead of "mdat" !!!!!!!!!!!!!
            throw new IOException("File is not 3GP. mdat header missing.");
        }
        // You can check if it is correct here
        int rawAmrDataLength = mdatHeader.getDataLength();
        System.out.println("RAW Amr length: "+bis.available());
        int fullAmrDataLength = AMR_MAGIC_HEADER.length + rawAmrDataLength;
        byte[] amrData = new byte[fullAmrDataLength];
        System.arraycopy(AMR_MAGIC_HEADER, 0, amrData, 0, AMR_MAGIC_HEADER.length);
        bis.read(amrData, AMR_MAGIC_HEADER.length, rawAmrDataLength);
        bis.close();

        //create raw amr file
        File rawAmrFile = new File(rawAmrFilePath);
        FileOutputStream fos = new FileOutputStream(rawAmrFile);    
        AMRFile amrFile = null;

        try {
            fos.write(amrData);
        } catch (Exception e) {
            Log.e(getClass().getName(), e.getMessage(), e);         
        }
        finally{
            fos.close();
            amrFile = new AMRFile(rawAmrFile);
        }

        System.out.println("AMR file length: "+amrFile.getRawFile().length());
        return amrFile;
    }
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1 に答える 1

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I used some HEX Viewer tool to look into my .3gp file and I saw that mdat box wasn't in the place where the algorithm has looked for, so I decided to read from the stream until I find the mdat box. Now the extraction works ok. I modified MediaDataBox a little bit:

public MediaDataBox(FileInputStream is) throws IOException {
        super(is);

        //check the mdat header - if not read until mdat if found
        long last32Int = 0;
        long curr32Int = 0;
        long temp;
        while (is.available()>=8) {
            temp = curr32Int = readUint32(is);          

            //test like this to avoid low memory issues
            if((HEADER_TYPE.charAt(0) == (byte)(temp >>> 24)) && 
                    (HEADER_TYPE.charAt(1) == (byte)(temp >>> 16)) &&
                        (HEADER_TYPE.charAt(2) == (byte)(temp >>> 8)) &&
                            (HEADER_TYPE.charAt(3) == (byte)temp)){

                size = last32Int;
                type = curr32Int;
                boxSize = 8;
                break;
            }
            last32Int = curr32Int;
        }
    }

and super class:

public _3GPBox(FileInputStream is) throws IOException{
        size = readUint32(is);
        boxSize += 4;
        type = readUint32(is);
        boxSize += 4;
    }
于 2013-07-10T13:36:54.320 に答える