每日聚焦：解析M3U8索引文件 下载M3U8视频文件的解析

M3U8文件是一个索引文件，里面包好N个TS的分片文件，组成一个视频文件。目前在直播和点播中应用非常广泛。我们下载一个M3U8视频文件，就是下载了N个TS分片文件，导致我们手机相册中多了很多碎片的小视频文件。如果是羞羞的视频，更加不好意思了。删除都要删除半天，更不用说想把M3U8文件拷贝出来，放到电脑上观看欣赏。

例如给一个M3U8例子，解析出来的索引文件如下：

(资料图)

#EXTM3U

#EXT-X-VERSION:3

#EXT-X-MEDIA-SEQUENCE:0

#EXT-X-ALLOW-CACHE:YES

#EXT-X-TARGETDURATION:19

#EXTINF:13.960000,

out000.ts

#EXTINF:6.320000,

out001.ts

#EXTINF:10.280000,

out002.ts

#EXTINF:10.320000,

out003.ts

#EXTINF:9.960000,

out004.ts

#EXTINF:12.240000,

out005.ts

#EXTINF:8.680000,

out006.ts

#EXTINF:8.280000,

out007.ts

#EXTINF:10.240000,

out008.ts

#EXTINF:15.000000,

out009.ts

#EXTINF:5.000000,

out010.ts

#EXTINF:14.200000,

out011.ts

#EXTINF:7.920000,

out012.ts

#EXTINF:8.920000,

out013.ts

#EXTINF:10.960000,

out014.ts

#EXTINF:7.920000,

out015.ts

#EXTINF:10.000000,

out016.ts

#EXTINF:12.040000,

out017.ts

#EXTINF:9.280000,

out018.ts

#EXTINF:17.160000,

out019.ts

#EXTINF:8.080000,

out020.ts

#EXTINF:6.840000,

out021.ts

#EXTINF:8.040000,

out022.ts

#EXTINF:11.640000,

out023.ts

#EXTINF:10.000000,

out024.ts

#EXTINF:7.760000,

out025.ts

#EXTINF:9.040000,

out026.ts

#EXTINF:13.760000,

out027.ts

#EXTINF:7.120000,

out028.ts

#EXTINF:10.560000,

out029.ts

#EXTINF:11.640000,

out030.ts

#EXTINF:7.880000,

out031.ts

#EXTINF:11.880000,

out032.ts

#EXTINF:12.640000,

out033.ts

#EXTINF:6.920000,

out034.ts

#EXTINF:8.320000,

out035.ts

#EXTINF:10.720000,

out036.ts

#EXTINF:8.840000,

out037.ts

#EXTINF:10.320000,

out038.ts

#EXTINF:9.760000,

out039.ts

#EXTINF:10.320000,

out040.ts

#EXTINF:10.800000,

out041.ts

#EXTINF:13.200000,

out042.ts

#EXTINF:7.480000,

out043.ts

#EXTINF:8.560000,

out044.ts

#EXTINF:10.160000,

out045.ts

#EXTINF:10.160000,

out046.ts

#EXTINF:9.360000,

out047.ts

#EXTINF:11.960000,

out048.ts

#EXTINF:10.640000,

out049.ts

#EXTINF:11.360000,

out050.ts

#EXTINF:8.040000,

out051.ts

#EXTINF:7.640000,

out052.ts

#EXTINF:10.480000,

out053.ts

#EXTINF:10.400000,

out054.ts

#EXTINF:9.360000,

out055.ts

#EXTINF:15.720000,

out056.ts

#EXTINF:4.600000,

out057.ts

#EXTINF:9.640000,

out058.ts

#EXTINF:17.800000,

out059.ts

#EXTINF:6.040000,

out060.ts

#EXTINF:9.400000,

out061.ts

#EXTINF:10.000000,

out062.ts

#EXTINF:10.000000,

out063.ts

#EXTINF:10.000000,

out064.ts

#EXTINF:10.000000,

out065.ts

#EXTINF:9.000000,

out066.ts

#EXTINF:10.000000,

out067.ts

#EXTINF:10.000000,

out068.ts

#EXTINF:8.920000,

out069.ts

#EXTINF:15.920000,

out070.ts

#EXTINF:5.200000,

out071.ts

#EXTINF:8.240000,

out072.ts

#EXTINF:13.200000,

out073.ts

#EXTINF:14.400000,

out074.ts

#EXTINF:8.960000,

out075.ts

#EXTINF:5.880000,

out076.ts

#EXTINF:10.000000,

out077.ts

#EXTINF:10.000000,

out078.ts

#EXTINF:6.720000,

out079.ts

#EXTINF:16.720000,

out080.ts

#EXTINF:10.000000,

out081.ts

#EXTINF:10.000000,

out082.ts

#EXTINF:10.000000,

out083.ts

#EXTINF:9.640000,

out084.ts

#EXTINF:9.080000,

out085.ts

#EXTINF:7.000000,

out086.ts

#EXTINF:10.000000,

out087.ts

#EXTINF:17.320000,

out088.ts

#EXTINF:9.920000,

out089.ts

#EXTINF:8.000000,

out090.ts

#EXTINF:6.040000,

out091.ts

#EXTINF:7.560000,

out092.ts

#EXTINF:10.000000,

out093.ts

#EXTINF:8.800000,

out094.ts

#EXTINF:10.000000,

out095.ts

#EXTINF:10.000000,

out096.ts

#EXTINF:12.200000,

out097.ts

#EXTINF:10.000000,

out098.ts

#EXTINF:17.240000,

out099.ts

#EXTINF:10.000000,

out100.ts

#EXTINF:9.680000,

out101.ts

#EXTINF:10.000000,

out102.ts

#EXTINF:10.000000,

out103.ts

#EXTINF:10.000000,

out104.ts

#EXTINF:10.000000,

out105.ts

#EXTINF:10.000000,

out106.ts

#EXTINF:10.000000,

out107.ts

#EXTINF:10.000000,

out108.ts

#EXTINF:9.080000,

out109.ts

#EXTINF:10.000000,

out110.ts

#EXTINF:10.000000,

out111.ts

#EXTINF:10.000000,

out112.ts

#EXTINF:10.000000,

out113.ts

#EXTINF:10.000000,

out114.ts

#EXTINF:10.000000,

out115.ts

#EXTINF:10.000000,

out116.ts

#EXTINF:6.040000,

out117.ts

#EXTINF:9.000000,

out118.ts

#EXTINF:10.000000,

out119.ts

#EXTINF:10.000000,

out120.ts

#EXTINF:10.000000,

out121.ts

#EXTINF:10.000000,

out122.ts

#EXTINF:10.000000,

out123.ts

#EXTINF:10.000000,

out124.ts

#EXTINF:10.000000,

out125.ts

#EXTINF:10.000000,

out126.ts

#EXTINF:10.000000,

out127.ts

#EXTINF:10.000000,

out128.ts

#EXTINF:10.000000,

out129.ts

#EXTINF:10.000000,

out130.ts

#EXTINF:10.000000,

out131.ts

#EXTINF:9.760000,

out132.ts

#EXTINF:10.000000,

out133.ts

#EXTINF:10.000000,

out134.ts

#EXTINF:10.000000,

out135.ts

#EXTINF:10.000000,

out136.ts

#EXTINF:10.000000,

out137.ts

#EXTINF:8.880000,

out138.ts

#EXTINF:9.240000,

out139.ts

#EXTINF:11.840000,

out140.ts

#EXTINF:10.000000,

out141.ts

#EXTINF:10.000000,

out142.ts

#EXTINF:8.280000,

out143.ts

#EXTINF:10.000000,

out144.ts

#EXTINF:16.400000,

out145.ts

#EXTINF:3.960000,

out146.ts

#EXTINF:10.160000,

out147.ts

#EXTINF:8.360000,

out148.ts

#EXTINF:11.160000,

out149.ts

#EXTINF:12.440000,

out150.ts

#EXTINF:7.520000,

out151.ts

#EXTINF:12.600000,

out152.ts

#EXTINF:14.400000,

out153.ts

#EXTINF:4.800000,

out154.ts

#EXTINF:13.280000,

out155.ts

#EXTINF:10.000000,

out156.ts

#EXTINF:6.520000,

out157.ts

#EXTINF:9.160000,

out158.ts

#EXTINF:10.000000,

out159.ts

#EXTINF:7.920000,

out160.ts

#EXTINF:17.960000,

out161.ts

#EXTINF:8.000000,

out162.ts

#EXTINF:10.000000,

out163.ts

#EXTINF:10.000000,

out164.ts

#EXTINF:8.680000,

out165.ts

#EXTINF:8.920000,

out166.ts

#EXTINF:15.880000,

out167.ts

#EXTINF:3.360000,

out168.ts

#EXTINF:11.200000,

out169.ts

#EXTINF:8.160000,

out170.ts

#EXTINF:10.920000,

out171.ts

#EXTINF:8.280000,

out172.ts

#EXTINF:8.640000,

out173.ts

#EXTINF:14.400000,

out174.ts

#EXTINF:10.000000,

out175.ts

#EXTINF:8.960000,

out176.ts

#EXTINF:10.000000,

out177.ts

#EXTINF:13.560000,

out178.ts

#EXTINF:10.000000,

out179.ts

#EXTINF:10.000000,

out180.ts

#EXTINF:10.000000,

out181.ts

#EXTINF:10.000000,

out182.ts

#EXTINF:10.000000,

out183.ts

#EXTINF:10.000000,

out184.ts

#EXTINF:10.000000,

out185.ts

#EXTINF:10.000000,

out186.ts

#EXTINF:10.000000,

out187.ts

#EXTINF:10.000000,

out188.ts

#EXTINF:10.000000,

out189.ts

#EXTINF:10.000000,

out190.ts

#EXTINF:10.000000,

out191.ts

#EXTINF:10.000000,

out192.ts

#EXTINF:10.000000,

out193.ts

#EXTINF:10.000000,

out194.ts

#EXTINF:9.200000,

out195.ts

#EXTINF:10.000000,

out196.ts

#EXTINF:10.000000,

out197.ts

#EXTINF:10.000000,

out198.ts

#EXTINF:8.720000,

out199.ts

#EXTINF:10.000000,

out200.ts

#EXTINF:13.040000,

out201.ts

#EXTINF:6.360000,

out202.ts

#EXTINF:10.000000,

out203.ts

#EXTINF:15.200000,

out204.ts

#EXTINF:7.960000,

out205.ts

#EXTINF:8.120000,

out206.ts

#EXTINF:10.000000,

out207.ts

#EXTINF:9.600000,

out208.ts

#EXTINF:9.720000,

out209.ts

#EXTINF:10.000000,

out210.ts

#EXTINF:10.000000,

out211.ts

#EXTINF:10.000000,

out212.ts

#EXTINF:9.160000,

out213.ts

#EXTINF:10.000000,

out214.ts

#EXTINF:10.000000,

out215.ts

#EXTINF:8.040000,

out216.ts

#EXTINF:10.000000,

out217.ts

#EXTINF:10.000000,

out218.ts

#EXTINF:10.000000,

out219.ts

#EXTINF:10.000000,

out220.ts

#EXTINF:10.000000,

out221.ts

#EXTINF:10.000000,

out222.ts

#EXTINF:10.000000,

out223.ts

#EXTINF:10.000000,

out224.ts

#EXTINF:8.240000,

out225.ts

#EXTINF:15.200000,

out226.ts

#EXTINF:6.200000,

out227.ts

#EXTINF:9.560000,

out228.ts

#EXTINF:10.000000,

out229.ts

#EXTINF:10.000000,

out230.ts

#EXTINF:10.000000,

out231.ts

#EXTINF:9.560000,

out232.ts

#EXTINF:9.640000,

out233.ts

#EXTINF:17.880000,

out234.ts

#EXTINF:8.600000,

out235.ts

#EXTINF:9.560000,

out236.ts

#EXTINF:10.000000,

out237.ts

#EXTINF:10.000000,

out238.ts

#EXTINF:8.000000,

out239.ts

#EXTINF:10.000000,

out240.ts

#EXTINF:10.000000,

out241.ts

#EXTINF:10.000000,

out242.ts

#EXTINF:10.000000,

out243.ts

#EXTINF:10.000000,

out244.ts

#EXTINF:10.000000,

out245.ts

#EXTINF:9.440000,

out246.ts

#EXTINF:14.240000,

out247.ts

#EXTINF:5.840000,

out248.ts

#EXTINF:6.600000,

out249.ts

#EXTINF:9.920000,

out250.ts

#EXTINF:11.080000,

out251.ts

#EXTINF:14.600000,

out252.ts

#EXTINF:7.160000,

out253.ts

#EXTINF:8.840000,

out254.ts

#EXTINF:11.320000,

out255.ts

#EXTINF:8.720000,

out256.ts

#EXTINF:8.240000,

out257.ts

#EXTINF:9.880000,

out258.ts

#EXTINF:18.480000,

out259.ts

#EXTINF:10.000000,

out260.ts

#EXTINF:8.760000,

out261.ts

#EXTINF:9.240000,

out262.ts

#EXTINF:6.120000,

out263.ts

#EXTINF:13.480000,

out264.ts

#EXTINF:10.000000,

out265.ts

#EXTINF:8.360000,

out266.ts

#EXTINF:6.080000,

out267.ts

#EXTINF:14.080000,

out268.ts

#EXTINF:7.520000,

out269.ts

#EXTINF:9.240000,

out270.ts

#EXTINF:10.000000,

out271.ts

#EXTINF:6.960000,

out272.ts

#EXT-X-ENDLIST

PD1824:/sdcard/Android/data/com.jeffmony.videodemo/files/Video/Download/a03663b3bd0a2fe6fcb8bb36b657cf80 $ ls

local.m3u8 video_124.ts video_152.ts video_180.ts video_208.ts video_236.ts video_264.ts video_47.ts video_75.ts

remote.m3u8 video_125.ts video_153.ts video_181.ts video_209.ts video_237.ts video_265.ts video_48.ts video_76.ts

video_0.ts video_126.ts video_154.ts video_182.ts video_21.ts video_238.ts video_266.ts video_49.ts video_77.ts

video_1.ts video_127.ts video_155.ts video_183.ts video_210.ts video_239.ts video_267.ts video_5.ts video_78.ts

video_10.ts video_128.ts video_156.ts video_184.ts video_211.ts video_24.ts video_268.ts video_50.ts video_79.ts

video_100.ts video_129.ts video_157.ts video_185.ts video_212.ts video_240.ts video_269.ts video_51.ts video_8.ts

video_101.ts video_13.ts video_158.ts video_186.ts video_213.ts video_241.ts video_27.ts video_52.ts video_80.ts

video_102.ts video_130.ts video_159.ts video_187.ts video_214.ts video_242.ts video_270.ts video_53.ts video_81.ts

video_103.ts video_131.ts video_16.ts video_188.ts video_215.ts video_243.ts video_271.ts video_54.ts video_82.ts

video_104.ts video_132.ts video_160.ts video_189.ts video_216.ts video_244.ts video_272.ts video_55.ts video_83.ts

video_105.ts video_133.ts video_161.ts video_19.ts video_217.ts video_245.ts video_28.ts video_56.ts video_84.ts

video_106.ts video_134.ts video_162.ts video_190.ts video_218.ts video_246.ts video_29.ts video_57.ts video_85.ts

video_107.ts video_135.ts video_163.ts video_191.ts video_219.ts video_247.ts video_3.ts video_58.ts video_86.ts

video_108.ts video_136.ts video_164.ts video_192.ts video_22.ts video_248.ts video_30.ts video_59.ts video_87.ts

video_109.ts video_137.ts video_165.ts video_193.ts video_220.ts video_249.ts video_31.ts video_6.ts video_88.ts

video_11.ts video_138.ts video_166.ts video_194.ts video_221.ts video_25.ts video_32.ts video_60.ts video_89.ts

video_110.ts video_139.ts video_167.ts video_195.ts video_222.ts video_250.ts video_33.ts video_61.ts video_9.ts

video_111.ts video_14.ts video_168.ts video_196.ts video_223.ts video_251.ts video_34.ts video_62.ts video_90.ts

video_112.ts video_140.ts video_169.ts video_197.ts video_224.ts video_252.ts video_35.ts video_63.ts video_91.ts

video_113.ts video_141.ts video_17.ts video_198.ts video_225.ts video_253.ts video_36.ts video_64.ts video_92.ts

video_114.ts video_142.ts video_170.ts video_199.ts video_226.ts video_254.ts video_37.ts video_65.ts video_93.ts

video_115.ts video_143.ts video_171.ts video_2.ts video_227.ts video_255.ts video_38.ts video_66.ts video_94.ts

video_116.ts video_144.ts video_172.ts video_20.ts video_228.ts video_256.ts video_39.ts video_67.ts video_95.ts

video_117.ts video_145.ts video_173.ts video_200.ts video_229.ts video_257.ts video_4.ts video_68.ts video_96.ts

video_118.ts video_146.ts video_174.ts video_201.ts video_23.ts video_258.ts video_40.ts video_69.ts video_97.ts

video_119.ts video_147.ts video_175.ts video_202.ts video_230.ts video_259.ts video_41.ts video_7.ts video_98.ts

video_12.ts video_148.ts video_176.ts video_203.ts video_231.ts video_26.ts video_42.ts video_70.ts video_99.ts

video_120.ts video_149.ts video_177.ts video_204.ts video_232.ts video_260.ts video_43.ts video_71.ts

video_121.ts video_15.ts video_178.ts video_205.ts video_233.ts video_261.ts video_44.ts video_72.ts

video_122.ts video_150.ts video_179.ts video_206.ts video_234.ts video_262.ts video_45.ts video_73.ts

video_123.ts video_151.ts video_18.ts video_207.ts video_235.ts video_263.ts video_46.ts video_74.ts

如果能将这些TS文件合成一个视频文件就好了。

TS文件合成一个MP4视频，需要的注意点有：

有些M3U8视频是加密的，TS源文件需要解密才能播放

TS文件一个个拼接的方式最后得到的还是一个TS视频，只不过比较大一点，并不是后缀名改成.mp4就是MP4视频了。

加密的视频

M3U8中的EXT-X-KEY中就包含M3U8的加密方式以及密钥。

例如http://video.yjf138.com:8091/20180812/6yl0Q2YZ/index.m3u8中就有

#EXT-X-KEY:METHOD=AES-128,URI="key.key"

可以看出加密方式是AES-128对称加密，密钥是key.key

转化为链接就是：https://video.yjf138.com:8091/20180812/6yl0Q2YZ/1500kb/hls/key.key

那我们就可以使用AES-128解密了，通常的做法是：

/**

* 解密ts

*

* @param sSrc ts文件字节数组

* @param sKey 密钥

* @return 解密后的字节数组

*/

private static byte[] decrypt(byte[] sSrc, String sKey, String method) {

try {

if (StringUtils.isNotEmpty(method) && !method.contains("AES")) {

throw new M3u8Exception("未知的算法！");

}

// 判断Key是否正确

if (StringUtils.isEmpty(sKey)) {

return sSrc;

}

// 判断Key是否为16位

if (sKey.length() != 16) {

System.out.print("Key长度不是16位");

return null;

}

Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");

SecretKeySpec keySpec = new SecretKeySpec(sKey.getBytes("utf-8"), "AES");

// 如果m3u8有IV标签，那么IvParameterSpec构造函数就把IV标签后的内容转成字节数组传进去

AlgorithmParameterSpec paramSpec = new IvParameterSpec(new byte[16]);

cipher.init(Cipher.DECRYPT_MODE, keySpec, paramSpec);

return cipher.doFinal(sSrc);

} catch (Exception ex) {

ex.printStackTrace();

return null;

}

}

但是在Android平台上，这样的写法并不能兼容所有的场景，因为不同Android level上面的crypto写法不同，调用系统的api得到的结果也会不一样，所以最好将解密场景放在native层，使用openssl库来帮我们实现解密。

TS转化为MP4

之前说过，TS合并通常的做法使用InputStream读取一个一个的TS分片，然后利用OutputStream写入本地的MP4文件中，这样看上去好像是生成了一个新的MP4文件，但是实际上这个新的视频是真正的MP4格式吗？

显然不是，因为MP4的封装格式和TS是完全不一样的。

最好的做法就是将最终生成的文件按照MP4的封装规则重写一遍，这样最终生成的文件肯定是MP4的文件。

我们不用对照MP4的位flag来一个个生成，只要借助ffmpeg来帮我们实现这个转化就可以了。

对源文件进行解封装处理，取出源文件的音频流和视频流

创建目标文件的封装格式头信息。

读取源文件音频流和视频流中的包数据、帧数据，然后按照规则封装到目标文件格式中。