mp4缓冲播放
情景描述
后台上传mp4文件到服务器，通过nginx代理静态资源MP4把访问地址参数提供给app。app用户反应，视频无法加载。或者加载过慢。（在chrome，firefox,360等众多浏览器直接访问mp4访问地址都是秒播）
mp4文件格式
moov对于MP4来说，就是目录，它是包含着mp4的元数据。moov模块存放着如下信息
1 视频包括编码等级、分辨率、色域、码率、帧率、位深、时长等等……
2 音频又包括声道、采样率等音频特有属性
mdat:媒体数据容器。存放mp4大内容的地方。
加载快慢的原因是（元数据模块的顺序和使用的访问方式）
1 秒播：chrome，firefox,360 很智能，如果读取MP4文件，发现moov box不在文件前部，会直接读取MP4的文件尾部，加载moov box
2 卡顿：Flash如果读取MP4文件，发现moov box不在文件前部，不会直接读取MP4的文件尾部去寻找moov box，所以Flash要等文件全部下载完，取到文件尾部的moov头，才可以正常播放。
3 流媒体服务器，即使moov在文件尾部 也会先发moov头出去给CDN或用户，相当于CDN回源，或者用户回源请求到的MP4，已经是moov头在文件头部的了，虽然 这个时候 源站存储的还是moov头在文件尾部的MP4。
综上所述：所以，如果安卓采用和flash一样的机制来顺序解析mp4文件，如果mp4文件的moov模块在mdat后面。那么就会造成卡顿！！！
解决办法：
知道了mp4播放的原理，我们只要保证。moov在mdat前面解析就行了。ps：修改mp4文件大模块的顺序，是不会影响这个文件整体效果的。
方法1：部署流媒体服务器，给安卓提供流媒体的播放地址。不再采用http地址访问MP4。（成本高，复杂，不考虑）
方法2：修改mp4文件的模块顺序。（修改mp4模块顺序的代码，可百度，nice）
方法3：安卓端修改解析mp4的顺序，先解析moov模块。（不懂安卓，不考虑）
附：修改mp4文件模块的代码(百度不到我也不会选择这个办法对吧 https://blog.****.net/lzh838330255/article/details/53286430)
package cc.ligu.mvc.common;
import java.io.*;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.FileChannel;
public class QtFastStart {
public static boolean sDEBUG = false;
private static void safeClose(Closeable closeable) {
if (closeable != null) {
try {
closeable.close();
} catch (IOException e) {
printe(e, "Failed to close file: ");
}
}
}
/* package */
static long uint32ToLong(int int32) {
return int32 & 0x00000000ffffffffL;
}
/**
* Ensures passed uint32 value in long can be represented as Java int.
*/
/* package */
static int uint32ToInt(int uint32) throws UnsupportedFileException {
if (uint32 < 0) {
throw new UnsupportedFileException("uint32 value is too large");
}
return uint32;
}
/**
* Ensures passed uint32 value in long can be represented as Java int.
*/
/* package */
static int uint32ToInt(long uint32) throws UnsupportedFileException {
if (uint32 > Integer.MAX_VALUE || uint32 < 0) {
throw new UnsupportedFileException("uint32 value is too large");
}
return (int) uint32;
}
/**
* Ensures passed uint64 value can be represented as Java long.
*/
/* package */
static long uint64ToLong(long uint64) throws UnsupportedFileException {
if (uint64 < 0) throw new UnsupportedFileException("uint64 value is too large");
return uint64;
}
private static int fourCcToInt(byte[] byteArray) {
return ByteBuffer.wrap(byteArray).order(ByteOrder.BIG_ENDIAN).getInt();
}
private static void printf(String format, Object... args) {
if (sDEBUG) System.err.println("QtFastStart: " + String.format(format, args));
}
private static void printe(Throwable e, String format, Object... args) {
printf(format, args);
if (sDEBUG) e.printStackTrace();
}
private static boolean readAndFill(FileChannel infile, ByteBuffer buffer) throws IOException {
buffer.clear();
int size = infile.read(buffer);
buffer.flip();
return size == buffer.capacity();
}
private static boolean readAndFill(FileChannel infile, ByteBuffer buffer, long position) throws IOException {
buffer.clear();
int size = infile.read(buffer, position);
buffer.flip();
return size == buffer.capacity();
}
/* top level atoms */
private static final int FREE_ATOM = fourCcToInt(new byte[]{'f', 'r', 'e', 'e'});
private static final int JUNK_ATOM = fourCcToInt(new byte[]{'j', 'u', 'n', 'k'});
private static final int MDAT_ATOM = fourCcToInt(new byte[]{'m', 'd', 'a', 't'});
private static final int MOOV_ATOM = fourCcToInt(new byte[]{'m', 'o', 'o', 'v'});
private static final int PNOT_ATOM = fourCcToInt(new byte[]{'p', 'n', 'o', 't'});
private static final int SKIP_ATOM = fourCcToInt(new byte[]{'s', 'k', 'i', 'p'});
private static final int WIDE_ATOM = fourCcToInt(new byte[]{'w', 'i', 'd', 'e'});
private static final int PICT_ATOM = fourCcToInt(new byte[]{'P', 'I', 'C', 'T'});
private static final int FTYP_ATOM = fourCcToInt(new byte[]{'f', 't', 'y', 'p'});
private static final int UUID_ATOM = fourCcToInt(new byte[]{'u', 'u', 'i', 'd'});
private static final int CMOV_ATOM = fourCcToInt(new byte[]{'c', 'm', 'o', 'v'});
private static final int STCO_ATOM = fourCcToInt(new byte[]{'s', 't', 'c', 'o'});
private static final int CO64_ATOM = fourCcToInt(new byte[]{'c', 'o', '6', '4'});
private static final int ATOM_PREAMBLE_SIZE = 8;
public static boolean fastStart(InputStream in, FileOutputStream out) throws IOException, MalformedFileException, UnsupportedFileException {
boolean ret = false;
FileInputStream inStream = (FileInputStream) in;
FileChannel infile = null;
FileChannel outfile= null;
try {
infile = inStream.getChannel();
outfile = out.getChannel();
return ret = fastStartImpl(infile, outfile);
} finally {
if (!ret) {
infile.transferTo(0, infile.size(), outfile);//当转换不成功时（正常是因文件小），直接copy.
// out.delete();
}else{
// in.delete();
}
safeClose(inStream);
safeClose(out);
}
}
/**
* @param in Input file.
* @param out Output file.
* @return false if input file is already fast start.
* @throws IOException
*/
public static boolean fastStart(String in, String out) throws IOException, MalformedFileException, UnsupportedFileException {
boolean ret = false;
FileInputStream inStream = null;
FileOutputStream outStream = null;
FileChannel infile = null;
FileChannel outfile= null;
try {
inStream = new FileInputStream(in);
infile = inStream.getChannel();
outStream = new FileOutputStream(out);
outfile = outStream.getChannel();
return ret = fastStartImpl(infile, outfile);
} finally {
if (!ret) {
infile.transferTo(0, infile.size(), outfile);//当转换不成功时（正常是因文件小），直接copy.
// out.delete();
}else{
// in.delete();
}
safeClose(inStream);
safeClose(outStream);
}
}
private static boolean fastStartImpl(FileChannel infile, FileChannel outfile) throws IOException, MalformedFileException, UnsupportedFileException {
ByteBuffer atomBytes = ByteBuffer.allocate(ATOM_PREAMBLE_SIZE).order(ByteOrder.BIG_ENDIAN);
int atomType = 0;
long atomSize = 0; // uint64_t
long lastOffset;
ByteBuffer moovAtom;
ByteBuffer ftypAtom = null;
// uint64_t, but assuming it is in int32 range. It is reasonable as int max is around 2GB. Such large moov is unlikely, yet unallocatable :).
int moovAtomSize;
long startOffset = 0;
System.out.println("QtFastStart------"+"开始");
// traverse through the atoms in the file to make sure that 'moov' is at the end
while (readAndFill(infile, atomBytes)) {
atomSize = uint32ToLong(atomBytes.getInt()); // uint32
atomType = atomBytes.getInt(); // representing uint32_t in signed int
// keep ftyp atom
if (atomType == FTYP_ATOM) {
int ftypAtomSize = uint32ToInt(atomSize); // XXX: assume in range of int32_t
ftypAtom = ByteBuffer.allocate(ftypAtomSize).order(ByteOrder.BIG_ENDIAN);
atomBytes.rewind();
ftypAtom.put(atomBytes);
if (infile.read(ftypAtom) < ftypAtomSize - ATOM_PREAMBLE_SIZE) break;
ftypAtom.flip();
startOffset = infile.position(); // after ftyp atom
System.out.println("QtFastStart---FTYP_ATOM---atomType:"+atomType);
System.out.println("QtFastStart---FTYP_ATOM---atomType:"+String.valueOf(infile.position()));
} else {
// System.out.println("QtFastStart------atomType:"+atomType);
if (atomSize == 1) {
/* 64-bit special case */
atomBytes.clear();
if (!readAndFill(infile, atomBytes)) break;
atomSize = uint64ToLong(atomBytes.getLong()); // XXX: assume in range of int64_t
infile.position(infile.position() + atomSize - ATOM_PREAMBLE_SIZE * 2); // seek
System.out.println("QtFastStart--atomSize == 1----atomType:"+atomType);
} else {
infile.position(infile.position() + atomSize - ATOM_PREAMBLE_SIZE); // seek
System.out.println("QtFastStart--else----atomType:"+atomType);
System.out.println("QtFastStart--else----atomType:"+String.valueOf(infile.position() + atomSize - ATOM_PREAMBLE_SIZE));
}
}
if (sDEBUG) printf("%c%c%c%c %10d %d",
(atomType >> 24) & 255,
(atomType >> 16) & 255,
(atomType >> 8) & 255,
(atomType >> 0) & 255,
infile.position() - atomSize,
atomSize);
if ((atomType != FREE_ATOM)
&& (atomType != JUNK_ATOM)
&& (atomType != MDAT_ATOM)
&& (atomType != MOOV_ATOM)
&& (atomType != PNOT_ATOM)
&& (atomType != SKIP_ATOM)
&& (atomType != WIDE_ATOM)
&& (atomType != PICT_ATOM)
&& (atomType != UUID_ATOM)
&& (atomType != FTYP_ATOM)) {
printf("encountered non-QT top-level atom (is this a QuickTime file?)");
break;
}
/* The atom header is 8 (or 16 bytes), if the atom size (which
* includes these 8 or 16 bytes) is less than that, we won't be
* able to continue scanning sensibly after this atom, so break. */
if (atomSize < 8)
break;
}
System.out.println("QtFastStart------"+"第一循环结束atomType:"+atomType);
if (atomType != MOOV_ATOM) {
printf("last atom in file was not a moov atom");
return false;
}
// moov atom was, in fact, the last atom in the chunk; load the whole moov atom
// atomSize is uint64, but for moov uint32 should be stored.
// XXX: assuming moov atomSize <= max vaue of int32
moovAtomSize = uint32ToInt(atomSize);
lastOffset = infile.size() - moovAtomSize; // NOTE: assuming no extra data after moov, as qt-faststart.c
moovAtom = ByteBuffer.allocate(moovAtomSize).order(ByteOrder.BIG_ENDIAN);
if (!readAndFill(infile, moovAtom, lastOffset)) {
throw new MalformedFileException("failed to read moov atom");
}
// this utility does not support compressed atoms yet, so disqualify files with compressed QT atoms
if (moovAtom.getInt(12) == CMOV_ATOM) {
throw new UnsupportedFileException("this utility does not support compressed moov atoms yet");
}
// crawl through the moov chunk in search of stco or co64 atoms
while (moovAtom.remaining() >= 8) {
int atomHead = moovAtom.position();
atomType = moovAtom.getInt(atomHead + 4); // representing uint32_t in signed int
if (!(atomType == STCO_ATOM || atomType == CO64_ATOM)) {
moovAtom.position(moovAtom.position() + 1);
continue;
}
atomSize = uint32ToLong(moovAtom.getInt(atomHead)); // uint32
if (atomSize > moovAtom.remaining()) {
throw new MalformedFileException("bad atom size");
}
moovAtom.position(atomHead + 12); // skip size (4 bytes), type (4 bytes), version (1 byte) and flags (3 bytes)
if (moovAtom.remaining() < 4) {
throw new MalformedFileException("malformed atom");
}
// uint32_t, but assuming moovAtomSize is in int32 range, so this will be in int32 range
int offsetCount = uint32ToInt(moovAtom.getInt());
if (atomType == STCO_ATOM) {
printf("patching stco atom...");
if (moovAtom.remaining() < offsetCount * 4) {
throw new MalformedFileException("bad atom size/element count");
}
for (int i = 0; i < offsetCount; i++) {
int currentOffset = moovAtom.getInt(moovAtom.position());
int newOffset = currentOffset + moovAtomSize; // calculate uint32 in int, bitwise addition
// current 0xffffffff => new 0x00000000 (actual >= 0x0000000100000000L)
if (currentOffset < 0 && newOffset >= 0) {
throw new UnsupportedFileException("This is bug in original qt-faststart.c: "
+ "stco atom should be extended to co64 atom as new offset value overflows uint32, "
+ "but is not implemented.");
}
moovAtom.putInt(newOffset);
}
} else if (atomType == CO64_ATOM) {
printf("patching co64 atom...");
if (moovAtom.remaining() < offsetCount * 8) {
throw new MalformedFileException("bad atom size/element count");
}
for (int i = 0; i < offsetCount; i++) {
long currentOffset = moovAtom.getLong(moovAtom.position());
moovAtom.putLong(currentOffset + moovAtomSize); // calculate uint64 in long, bitwise addition
}
}
}
infile.position(startOffset); // seek after ftyp atom
if (ftypAtom != null) {
// dump the same ftyp atom
printf("writing ftyp atom...");
ftypAtom.rewind();
outfile.write(ftypAtom);
}
// dump the new moov atom
printf("writing moov atom...");
moovAtom.rewind();
outfile.write(moovAtom);
// copy the remainder of the infile, from offset 0 -> (lastOffset - startOffset) - 1
printf("copying rest of file...");
infile.transferTo(startOffset, lastOffset - startOffset, outfile);
System.out.println("QtFastStart------"+"处理完成");
return true;
}
public static class QtFastStartException extends Exception {
private QtFastStartException(String detailMessage) {
super(detailMessage);
}
}
public static class MalformedFileException extends QtFastStartException {
private MalformedFileException(String detailMessage) {
super(detailMessage);
}
}
public static class UnsupportedFileException extends QtFastStartException {
private UnsupportedFileException(String detailMessage) {
super(detailMessage);
}
}
public static void main(String[] args) {
try {
String path = "C:\\Users\\shenyy\\Desktop\\待转换视频\\1540710345332.mp4";
InputStream in = new FileInputStream(path);
FileOutputStream out = new FileOutputStream(path+"_");
boolean success = QtFastStart.fastStart(in, out);
} catch (IOException e) {
e.printStackTrace();
} catch (MalformedFileException e) {
e.printStackTrace();
} catch (UnsupportedFileException e) {
e.printStackTrace();
}
}
}
附：视频转换前后的模块顺序对比 1前。2后
1
2
很明显，同一个文件，模块顺序变了，使用flash播放，moov在前的明显秒播。
效果
附 mp4文件详细格式