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android ijkplayer c层分析-初始化(续1 java层与c层衔接)

Olivia / 1713人阅读

摘要:初始化的过程上一篇其实并未完全分析完,这回接着来。层的函数中,最后还有的调用,走的是层的。结构体如下的和,以及,其余是状态及的内容。整个过程是个异步的过程,并不阻塞。至于的东西,都是在层创建并填充的。

初始化的过程上一篇其实并未完全分析完,这回接着来。java层的initPlayer函数中,最后还有native_setup的调用,走的是c层的IjkMediaPlayer_native_setup。来看看他干了什么吧:

</>复制代码

  1. IjkMediaPlayer_native_setup(JNIEnv *env, jobject thiz, jobject weak_this)
  2. {
  3. MPTRACE("%s
  4. ", __func__);
  5. IjkMediaPlayer *mp = ijkmp_android_create(message_loop);
  6. JNI_CHECK_GOTO(mp, env, "java/lang/OutOfMemoryError", "mpjni: native_setup: ijkmp_create() failed", LABEL_RETURN);
  7. jni_set_media_player(env, thiz, mp);
  8. ijkmp_set_weak_thiz(mp, (*env)->NewGlobalRef(env, weak_this));
  9. ijkmp_set_inject_opaque(mp, ijkmp_get_weak_thiz(mp));
  10. ijkmp_android_set_mediacodec_select_callback(mp, mediacodec_select_callback, ijkmp_get_weak_thiz(mp));
  11. LABEL_RETURN:
  12. ijkmp_dec_ref_p(&mp);
  13. }

首先创建播放器IjkMediaPlayer,传入一个message_loop。继续看ijkmp_android_create:

</>复制代码

  1. IjkMediaPlayer *ijkmp_android_create(int(*msg_loop)(void*))
  2. {
  3. IjkMediaPlayer *mp = ijkmp_create(msg_loop);
  4. if (!mp)
  5. goto fail;
  6. mp->ffplayer->vout = SDL_VoutAndroid_CreateForAndroidSurface();
  7. if (!mp->ffplayer->vout)
  8. goto fail;
  9. mp->ffplayer->pipeline = ffpipeline_create_from_android(mp->ffplayer);
  10. if (!mp->ffplayer->pipeline)
  11. goto fail;
  12. ffpipeline_set_vout(mp->ffplayer->pipeline, mp->ffplayer->vout);
  13. return mp;
  14. fail:
  15. ijkmp_dec_ref_p(&mp);
  16. return NULL;
  17. }

好吧,往下继续看ijkmp_create:

</>复制代码

  1. IjkMediaPlayer *ijkmp_create(int (*msg_loop)(void*))
  2. {
  3. IjkMediaPlayer *mp = (IjkMediaPlayer *) mallocz(sizeof(IjkMediaPlayer));
  4. if (!mp)
  5. goto fail;
  6. mp->ffplayer = ffp_create();
  7. if (!mp->ffplayer)
  8. goto fail;
  9. mp->msg_loop = msg_loop;
  10. ijkmp_inc_ref(mp);
  11. pthread_mutex_init(&mp->mutex, NULL);
  12. return mp;
  13. fail:
  14. ijkmp_destroy_p(&mp);
  15. return NULL;
  16. }

一上来为结构体IjkMediaPlayer分配空间,然后填充里面的内容,例如ffplayer和msg_loop。结构体如下:

</>复制代码

  1. struct IjkMediaPlayer {
  2. volatile int ref_count;
  3. pthread_mutex_t mutex;
  4. FFPlayer *ffplayer;
  5. int (*msg_loop)(void*);
  6. SDL_Thread *msg_thread;
  7. SDL_Thread _msg_thread;
  8. int mp_state;
  9. char *data_source;
  10. void *weak_thiz;
  11. int restart;
  12. int restart_from_beginning;
  13. int seek_req;
  14. long seek_msec;
  15. };

ffmpeg的player和sdl,以及msg_loop,其余是状态及seek的内容。
回来到ijkmp_create。看这里将这个函数指针给了mp的msg_loop。然后是ijkmp_inc_ref,这里设置了mp的引用计数加1。好吧,先回来看下这个loop是什么东西,回到最初的IjkMediaPlayer_native_setup。

</>复制代码

  1. static int message_loop(void *arg)
  2. {
  3. MPTRACE("%s
  4. ", __func__);
  5. JNIEnv *env = NULL;
  6. (*g_jvm)->AttachCurrentThread(g_jvm, &env, NULL );
  7. IjkMediaPlayer *mp = (IjkMediaPlayer*) arg;
  8. JNI_CHECK_GOTO(mp, env, NULL, "mpjni: native_message_loop: null mp", LABEL_RETURN);
  9. message_loop_n(env, mp);
  10. LABEL_RETURN:
  11. ijkmp_dec_ref_p(&mp);
  12. (*g_jvm)->DetachCurrentThread(g_jvm);
  13. MPTRACE("message_loop exit");
  14. return 0;
  15. }

AttachCurrentThread为了获取JNIEnv,然后关键点是message_loop_n:

</>复制代码

  1. static void message_loop_n(JNIEnv *env, IjkMediaPlayer *mp)
  2. {
  3. jobject weak_thiz = (jobject) ijkmp_get_weak_thiz(mp);
  4. JNI_CHECK_GOTO(weak_thiz, env, NULL, "mpjni: message_loop_n: null weak_thiz", LABEL_RETURN);
  5. while (1) {
  6. AVMessage msg;
  7. int retval = ijkmp_get_msg(mp, &msg, 1);
  8. if (retval < 0)
  9. break;
  10. // block-get should never return 0
  11. assert(retval > 0);
  12. switch (msg.what) {
  13. case FFP_MSG_FLUSH:
  14. MPTRACE("FFP_MSG_FLUSH:
  15. ");
  16. post_event(env, weak_thiz, MEDIA_NOP, 0, 0);
  17. break;
  18. case FFP_MSG_ERROR:
  19. MPTRACE("FFP_MSG_ERROR: %d
  20. ", msg.arg1);
  21. post_event(env, weak_thiz, MEDIA_ERROR, MEDIA_ERROR_IJK_PLAYER, msg.arg1);
  22. break;
  23. case FFP_MSG_PREPARED:
  24. MPTRACE("FFP_MSG_PREPARED:
  25. ");
  26. post_event(env, weak_thiz, MEDIA_PREPARED, 0, 0);
  27. break;
  28. case FFP_MSG_COMPLETED:
  29. MPTRACE("FFP_MSG_COMPLETED:
  30. ");
  31. post_event(env, weak_thiz, MEDIA_PLAYBACK_COMPLETE, 0, 0);
  32. break;
  33. case FFP_MSG_VIDEO_SIZE_CHANGED:
  34. MPTRACE("FFP_MSG_VIDEO_SIZE_CHANGED: %d, %d
  35. ", msg.arg1, msg.arg2);
  36. post_event(env, weak_thiz, MEDIA_SET_VIDEO_SIZE, msg.arg1, msg.arg2);
  37. break;
  38. case FFP_MSG_SAR_CHANGED:
  39. MPTRACE("FFP_MSG_SAR_CHANGED: %d, %d
  40. ", msg.arg1, msg.arg2);
  41. post_event(env, weak_thiz, MEDIA_SET_VIDEO_SAR, msg.arg1, msg.arg2);
  42. break;
  43. case FFP_MSG_VIDEO_RENDERING_START:
  44. MPTRACE("FFP_MSG_VIDEO_RENDERING_START:
  45. ");
  46. post_event(env, weak_thiz, MEDIA_INFO, MEDIA_INFO_VIDEO_RENDERING_START, 0);
  47. break;
  48. case FFP_MSG_AUDIO_RENDERING_START:
  49. MPTRACE("FFP_MSG_AUDIO_RENDERING_START:
  50. ");
  51. post_event(env, weak_thiz, MEDIA_INFO, MEDIA_INFO_AUDIO_RENDERING_START, 0);
  52. break;
  53. case FFP_MSG_VIDEO_ROTATION_CHANGED:
  54. MPTRACE("FFP_MSG_VIDEO_ROTATION_CHANGED: %d
  55. ", msg.arg1);
  56. post_event(env, weak_thiz, MEDIA_INFO, MEDIA_INFO_VIDEO_ROTATION_CHANGED, msg.arg1);
  57. break;
  58. case FFP_MSG_BUFFERING_START:
  59. MPTRACE("FFP_MSG_BUFFERING_START:
  60. ");
  61. post_event(env, weak_thiz, MEDIA_INFO, MEDIA_INFO_BUFFERING_START, 0);
  62. break;
  63. case FFP_MSG_BUFFERING_END:
  64. MPTRACE("FFP_MSG_BUFFERING_END:
  65. ");
  66. post_event(env, weak_thiz, MEDIA_INFO, MEDIA_INFO_BUFFERING_END, 0);
  67. break;
  68. case FFP_MSG_BUFFERING_UPDATE:
  69. // MPTRACE("FFP_MSG_BUFFERING_UPDATE: %d, %d", msg.arg1, msg.arg2);
  70. post_event(env, weak_thiz, MEDIA_BUFFERING_UPDATE, msg.arg1, msg.arg2);
  71. break;
  72. case FFP_MSG_BUFFERING_BYTES_UPDATE:
  73. break;
  74. case FFP_MSG_BUFFERING_TIME_UPDATE:
  75. break;
  76. case FFP_MSG_SEEK_COMPLETE:
  77. MPTRACE("FFP_MSG_SEEK_COMPLETE:
  78. ");
  79. post_event(env, weak_thiz, MEDIA_SEEK_COMPLETE, 0, 0);
  80. break;
  81. case FFP_MSG_PLAYBACK_STATE_CHANGED:
  82. break;
  83. case FFP_MSG_TIMED_TEXT:
  84. if (msg.obj) {
  85. jstring text = (*env)->NewStringUTF(env, (char *)msg.obj);
  86. post_event2(env, weak_thiz, MEDIA_TIMED_TEXT, 0, 0, text);
  87. J4A_DeleteLocalRef__p(env, &text);
  88. }
  89. else {
  90. post_event2(env, weak_thiz, MEDIA_TIMED_TEXT, 0, 0, NULL);
  91. }
  92. break;
  93. default:
  94. ALOGE("unknown FFP_MSG_xxx(%d)
  95. ", msg.what);
  96. break;
  97. }
  98. msg_free_res(&msg);
  99. }
  100. LABEL_RETURN:
  101. ;
  102. }

这明显是个事件处理loop,关键是post_event,里面就一句话:J4AC_IjkMediaPlayer__postEventFromNative(env, weak_this, what, arg1, arg2, NULL);最后追到J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer__postEventFromNative,里面是(*env)->CallStaticVoidMethod(env, class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.id, class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.method_postEventFromNative, weakThiz, what, arg1, arg2, obj);调用java层的函数,再看下去:J4A_loadClass__J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer里面:

</>复制代码

  1. class_id = class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.id;
  2. name = "postEventFromNative";
  3. sign = "(Ljava/lang/Object;IIILjava/lang/Object;)V";
  4. class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.method_postEventFromNative = J4A_GetStaticMethodID__catchAll(env, class_id, name, sign);
  5. if (class_J4AC_tv_danmaku_ijk_media_player_IjkMediaPlayer.method_postEventFromNative == NULL)
  6. goto fail;

不用说了吧,走的是java层的函数postEventFromNative。

</>复制代码

  1. @CalledByNative
  2. private static void postEventFromNative(Object weakThiz, int what,
  3. int arg1, int arg2, Object obj) {
  4. if (weakThiz == null)
  5. return;
  6. @SuppressWarnings("rawtypes")
  7. IjkMediaPlayer mp = (IjkMediaPlayer) ((WeakReference) weakThiz).get();
  8. if (mp == null) {
  9. return;
  10. }
  11. if (what == MEDIA_INFO && arg1 == MEDIA_INFO_STARTED_AS_NEXT) {
  12. // this acquires the wakelock if needed, and sets the client side
  13. // state
  14. mp.start();
  15. }
  16. if (mp.mEventHandler != null) {
  17. Message m = mp.mEventHandler.obtainMessage(what, arg1, arg2, obj);
  18. mp.mEventHandler.sendMessage(m);
  19. }
  20. }

这里把弱引用的IjkMediaPlayer取出来了,然后调用了mp.mEventHandler.sendMessage(m);那么这个IjkMediaPlayer是哪里来的呢?答案就在IjkMediaPlayer_native_setup,也就是java层的native_setup函数中传递进去的,在最初的initPlayer函数中调用的。那么java层的postEventFromNative里面的mp.mEventHandler是什么呢?就是initPlayer里面创建的looper。这下子串起来了吧,java层建立的IjkMediaPlayer,并填充eventhandler,c层在触发特定的一些动作(例如打开直播等),会调用java层的函数向looper里面发送message,于是java层就收到了内容,可以进行相关处理了。整个过程是个异步的过程,并不阻塞。至于ffmpeg的东西,都是在c层创建并填充的。

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