android ijkplayer c層分析-初始化
原本這個過程我是不大想寫初始化的過程，以爲網上已經有很多文章來分析了。可是在前面的整個分析過程當中，暴露了本身對一些問題理解還不夠透徹，所以有必要作一次。
首先是java層：java
private void initPlayer(IjkLibLoader libLoader) {
loadLibrariesOnce(libLoader);
initNativeOnce();
Looper looper;
if ((looper = Looper.myLooper()) != null) {
mEventHandler = new EventHandler(this, looper);
} else if ((looper = Looper.getMainLooper()) != null) {
mEventHandler = new EventHandler(this, looper);
} else {
mEventHandler = null;
}
/*
* Native setup requires a weak reference to our object. It's easier to
* create it here than in C++.
*/
native_setup(new WeakReference<IjkMediaPlayer>(this));
}
其實就2個事情，一個是loadLibrariesOnce，一個是initNativeOnce。前者的代碼就不貼了，就是loadLibrary3個so，分別是ijkffmpeg、ijksdl和ijkplayer。ffmpeg管協議和編解碼，sdl管渲染顯示，ijkplayer管理播放器。每次調用loadLibrary都會走到每一個so的JNI_OnLoad函數，也就是說這3個so的最開始初始化都在JNI_OnLoad這個函數內處理。回頭咱們再看；後者的initNativeOnce裏面實際上走的是native_init。這個對應的是jni的函數IjkMediaPlayer_native_init。在ijkplayer_jni.c中：網絡
static void
IjkMediaPlayer_native_init(JNIEnv *env)
{
MPTRACE("%s\n", __func__);
}
什麼都沒幹，對吧。
回來，看看JNI_OnLoad都幹了什麼：數據結構
JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved)
{
JNIEnv* env = NULL;
g_jvm = vm;
if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {
return -1;
}
assert(env != NULL);
pthread_mutex_init(&g_clazz.mutex, NULL );
// FindClass returns LocalReference
IJK_FIND_JAVA_CLASS(env, g_clazz.clazz, JNI_CLASS_IJKPLAYER);
(*env)->RegisterNatives(env, g_clazz.clazz, g_methods, NELEM(g_methods) );
ijkmp_global_init();
ijkmp_global_set_inject_callback(inject_callback);
FFmpegApi_global_init(env);
return JNI_VERSION_1_4;
}
前面都是通用的一些作法，主要是註冊函數表，用來在java層可以調用c層的函數。而後是ijkmp_global_init，這個最後會走到ffp_global_init：app
void ffp_global_init()
{
if (g_ffmpeg_global_inited)
return;
/* register all codecs, demux and protocols */
avcodec_register_all();
#if CONFIG_AVDEVICE
avdevice_register_all();
#endif
#if CONFIG_AVFILTER
avfilter_register_all();
#endif
av_register_all();
ijkav_register_all();
avformat_network_init();
av_lockmgr_register(lockmgr);
av_log_set_callback(ffp_log_callback_brief);
av_init_packet(&flush_pkt);
flush_pkt.data = (uint8_t *)&flush_pkt;
g_ffmpeg_global_inited = true;
}
基本上以ffmpeg的初始化內容居多，av開頭的應該都是。註冊解碼器，而後協議的註冊。咱們看ijkav_register_all：less
void ijkav_register_all(void)
{
static int initialized;
if (initialized)
return;
initialized = 1;
av_register_all();
/* protocols */
av_log(NULL, AV_LOG_INFO, "===== custom modules begin =====\n");
#ifdef __ANDROID__
IJK_REGISTER_PROTOCOL(ijkmediadatasource);
#endif
IJK_REGISTER_PROTOCOL(async);
IJK_REGISTER_PROTOCOL(ijklongurl);
IJK_REGISTER_PROTOCOL(ijktcphook);
IJK_REGISTER_PROTOCOL(ijkhttphook);
IJK_REGISTER_PROTOCOL(ijksegment);
/* demuxers */
IJK_REGISTER_DEMUXER(ijklivehook);
av_log(NULL, AV_LOG_INFO, "===== custom modules end =====\n");
}
基本上都是爲了支持網絡傳輸的協議註冊。而後是avformat_network_init，ffmpeg的網絡初始化。最後到達ff_network_init，裏面就是個WSAStartup。
回來看這麼多協議的註冊，先看下這個宏：jvm
#define IJK_REGISTER_PROTOCOL(x) \
{ \
extern URLProtocol ijkimp_ff_##x##_protocol; \
int ijkav_register_##x##_protocol(URLProtocol *protocol, int protocol_size);\
ijkav_register_##x##_protocol(&ijkimp_ff_##x##_protocol, sizeof(URLProtocol)); \
}
URLProtocol結構是個關鍵。那麼這個結構的填充靠什麼呢？看宏的調用，找到extern後面的部分，搜索下，原來在很多文件裏都有，例如ijkurlhook.c文件中：async
URLProtocol ijkimp_ff_ijktcphook_protocol = {
.name = "ijktcphook",
.url_open2 = ijktcphook_open,
.url_read = ijkurlhook_read,
.url_write = ijkurlhook_write,
.url_close = ijkurlhook_close,
.priv_data_size = sizeof(Context),
.priv_data_class = &ijktcphook_context_class,
};
這裏已經規定了打開和寫入關閉等的函數。這下子與基礎協議對應的各項操做算是找到了。咱們來看看不同的live的處理：tcp
#define IJK_REGISTER_DEMUXER(x) \
{ \
extern AVInputFormat ijkff_##x##_demuxer; \
ijkav_register_input_format(&ijkff_##x##_demuxer); \
}
而後會定位到ijklivehook.c文件中的ide
AVInputFormat ijkff_ijklivehook_demuxer = {
.name = "ijklivehook",
.long_name = "Live Hook Controller",
.flags = AVFMT_NOFILE | AVFMT_TS_DISCONT,
.priv_data_size = sizeof(Context),
.read_probe = ijklivehook_probe,
.read_header2 = ijklivehook_read_header,
.read_packet = ijklivehook_read_packet,
.read_close = ijklivehook_read_close,
.priv_class = &ijklivehook_class,
};
往下看，以ijklivehook_read_header爲例，能夠看到內部有url的判斷，區分rtmp和rtsp，這下子清楚了吧。
簡單總結一下，就是經過URLProtocol這個結構來規範化全部的協議，名稱和操做函數都在這裏定義。
回到ffp_global_init，下面進行到了av_init_packet。這裏插一下一個數據結構AVPacket。這個是存儲壓縮編碼數據相關信息的結構體。函數
typedef struct AVPacket {
/**
* A reference to the reference-counted buffer where the packet data is
* stored.
* May be NULL, then the packet data is not reference-counted.
*/
AVBufferRef *buf;
/**
* Presentation timestamp in AVStream->time_base units; the time at which
* the decompressed packet will be presented to the user.
* Can be AV_NOPTS_VALUE if it is not stored in the file.
* pts MUST be larger or equal to dts as presentation cannot happen before
* decompression, unless one wants to view hex dumps. Some formats misuse
* the terms dts and pts/cts to mean something different. Such timestamps
* must be converted to true pts/dts before they are stored in AVPacket.
*/
int64_t pts;
/**
* Decompression timestamp in AVStream->time_base units; the time at which
* the packet is decompressed.
* Can be AV_NOPTS_VALUE if it is not stored in the file.
*/
int64_t dts;
uint8_t *data;
int size;
int stream_index;
/**
* A combination of AV_PKT_FLAG values
*/
int flags;
/**
* Additional packet data that can be provided by the container.
* Packet can contain several types of side information.
*/
AVPacketSideData *side_data;
int side_data_elems;
/**
* Duration of this packet in AVStream->time_base units, 0 if unknown.
* Equals next_pts - this_pts in presentation order.
*/
int64_t duration;
int64_t pos; ///< byte position in stream, -1 if unknown
#if FF_API_CONVERGENCE_DURATION
/**
* @deprecated Same as the duration field, but as int64_t. This was required
* for Matroska subtitles, whose duration values could overflow when the
* duration field was still an int.
*/
attribute_deprecated
int64_t convergence_duration;
#endif
} AVPacket;
看到了什麼嗎？pts,dts,data。顯示時間戳，解碼時間戳，數據。av_init_packet就是個簡單填充，不貼代碼了。回到JNI_OnLoad，而後進行的是ijkmp_global_set_inject_callback。
設置了一個回調，那麼看看具體回調的約定吧：
static int
inject_callback(void *opaque, int what, void *data, size_t data_size)
{
JNIEnv *env = NULL;
jobject jbundle = NULL;
int ret = -1;
SDL_JNI_SetupThreadEnv(&env);
jobject weak_thiz = (jobject) opaque;
if (weak_thiz == NULL )
goto fail;
switch (what) {
case AVAPP_CTRL_WILL_HTTP_OPEN:
case AVAPP_CTRL_WILL_LIVE_OPEN:
case AVAPP_CTRL_WILL_CONCAT_SEGMENT_OPEN: {
AVAppIOControl *real_data = (AVAppIOControl *)data;
real_data->is_handled = 0;
jbundle = J4AC_Bundle__Bundle__catchAll(env);
if (!jbundle) {
ALOGE("%s: J4AC_Bundle__Bundle__catchAll failed for case %d\n", __func__, what);
goto fail;
}
J4AC_Bundle__putString__withCString__catchAll(env, jbundle, "url", real_data->url);
J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "segment_index", real_data->segment_index);
J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "retry_counter", real_data->retry_counter);
real_data->is_handled = J4AC_IjkMediaPlayer__onNativeInvoke(env, weak_thiz, what, jbundle);
if (J4A_ExceptionCheck__catchAll(env)) {
goto fail;
}
J4AC_Bundle__getString__withCString__asCBuffer(env, jbundle, "url", real_data->url, sizeof(real_data->url));
if (J4A_ExceptionCheck__catchAll(env)) {
goto fail;
}
ret = 0;
break;
}
case AVAPP_EVENT_WILL_HTTP_OPEN:
case AVAPP_EVENT_DID_HTTP_OPEN:
case AVAPP_EVENT_WILL_HTTP_SEEK:
case AVAPP_EVENT_DID_HTTP_SEEK: {
AVAppHttpEvent *real_data = (AVAppHttpEvent *) data;
jbundle = J4AC_Bundle__Bundle__catchAll(env);
if (!jbundle) {
ALOGE("%s: J4AC_Bundle__Bundle__catchAll failed for case %d\n", __func__, what);
goto fail;
}
J4AC_Bundle__putString__withCString__catchAll(env, jbundle, "url", real_data->url);
J4AC_Bundle__putLong__withCString__catchAll(env, jbundle, "offset", real_data->offset);
J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "error", real_data->error);
J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "http_code", real_data->http_code);
J4AC_IjkMediaPlayer__onNativeInvoke(env, weak_thiz, what, jbundle);
if (J4A_ExceptionCheck__catchAll(env))
goto fail;
ret = 0;
break;
}
case AVAPP_CTRL_DID_TCP_OPEN:
case AVAPP_CTRL_WILL_TCP_OPEN: {
AVAppTcpIOControl *real_data = (AVAppTcpIOControl *)data;
jbundle = J4AC_Bundle__Bundle__catchAll(env);
if (!jbundle) {
ALOGE("%s: J4AC_Bundle__Bundle__catchAll failed for case %d\n", __func__, what);
goto fail;
}
J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "error", real_data->error);
J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "family", real_data->family);
J4AC_Bundle__putString__withCString__catchAll(env, jbundle, "ip", real_data->ip);
J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "port", real_data->port);
J4AC_Bundle__putInt__withCString__catchAll(env, jbundle, "fd", real_data->fd);
J4AC_IjkMediaPlayer__onNativeInvoke(env, weak_thiz, what, jbundle);
if (J4A_ExceptionCheck__catchAll(env))
goto fail;
ret = 0;
break;
}
default: {
ret = 0;
}
}
fail:
SDL_JNI_DeleteLocalRefP(env, &jbundle);
return ret;
}
簡單找個函數看下：J4AC_IjkMediaPlayer__onNativeInvoke，在java層裏找到了定義：
private OnNativeInvokeListener mOnNativeInvokeListener;
public void setOnNativeInvokeListener(OnNativeInvokeListener listener) {
mOnNativeInvokeListener = listener;
}
public interface OnNativeInvokeListener {
int CTRL_WILL_TCP_OPEN = 0x20001; // NO ARGS
int CTRL_DID_TCP_OPEN = 0x20002; // ARG_ERROR, ARG_FAMILIY, ARG_IP, ARG_PORT, ARG_FD
int CTRL_WILL_HTTP_OPEN = 0x20003; // ARG_URL, ARG_SEGMENT_INDEX, ARG_RETRY_COUNTER
int CTRL_WILL_LIVE_OPEN = 0x20005; // ARG_URL, ARG_RETRY_COUNTER
int CTRL_WILL_CONCAT_RESOLVE_SEGMENT = 0x20007; // ARG_URL, ARG_SEGMENT_INDEX, ARG_RETRY_COUNTER
int EVENT_WILL_HTTP_OPEN = 0x1; // ARG_URL
int EVENT_DID_HTTP_OPEN = 0x2; // ARG_URL, ARG_ERROR, ARG_HTTP_CODE
int EVENT_WILL_HTTP_SEEK = 0x3; // ARG_URL, ARG_OFFSET
int EVENT_DID_HTTP_SEEK = 0x4; // ARG_URL, ARG_OFFSET, ARG_ERROR, ARG_HTTP_CODE
String ARG_URL = "url";
String ARG_SEGMENT_INDEX = "segment_index";
String ARG_RETRY_COUNTER = "retry_counter";
String ARG_ERROR = "error";
String ARG_FAMILIY = "family";
String ARG_IP = "ip";
String ARG_PORT = "port";
String ARG_FD = "fd";
String ARG_OFFSET = "offset";
String ARG_HTTP_CODE = "http_code";
/*
* @return true if invoke is handled
* @throws Exception on any error
*/
boolean onNativeInvoke(int what, Bundle args);
}
@CalledByNative
private static boolean onNativeInvoke(Object weakThiz, int what, Bundle args) {
DebugLog.ifmt(TAG, "onNativeInvoke %d", what);
if (weakThiz == null || !(weakThiz instanceof WeakReference<?>))
throw new IllegalStateException("<null weakThiz>.onNativeInvoke()");
@SuppressWarnings("unchecked")
WeakReference<IjkMediaPlayer> weakPlayer = (WeakReference<IjkMediaPlayer>) weakThiz;
IjkMediaPlayer player = weakPlayer.get();
if (player == null)
throw new IllegalStateException("<null weakPlayer>.onNativeInvoke()");
OnNativeInvokeListener listener = player.mOnNativeInvokeListener;
if (listener != null && listener.onNativeInvoke(what, args))
return true;
switch (what) {
case OnNativeInvokeListener.CTRL_WILL_CONCAT_RESOLVE_SEGMENT: {
OnControlMessageListener onControlMessageListener = player.mOnControlMessageListener;
if (onControlMessageListener == null)
return false;
int segmentIndex = args.getInt(OnNativeInvokeListener.ARG_SEGMENT_INDEX, -1);
if (segmentIndex < 0)
throw new InvalidParameterException("onNativeInvoke(invalid segment index)");
String newUrl = onControlMessageListener.onControlResolveSegmentUrl(segmentIndex);
if (newUrl == null)
throw new RuntimeException(new IOException("onNativeInvoke() = <NULL newUrl>"));
args.putString(OnNativeInvokeListener.ARG_URL, newUrl);
return true;
}
default:
return false;
}
}
那麼能夠肯定，這裏是註冊的回調，以便通知java層。好吧，回來繼續JNI_OnLoad，就差FFmpegApi_global_init了：
#define JNI_CLASS_FFMPEG_API "tv/danmaku/ijk/media/player/ffmpeg/FFmpegApi"
......
int FFmpegApi_global_init(JNIEnv *env)
{
int ret = 0;
IJK_FIND_JAVA_CLASS(env, g_clazz.clazz, JNI_CLASS_FFMPEG_API);
(*env)->RegisterNatives(env, g_clazz.clazz, g_methods, NELEM(g_methods));
return ret;
}
按照定義，找到這個類，只有一句話：
public class FFmpegApi {
public static native String av_base64_encode(byte in[]);
}
其實就是個base64的解碼，指向ffmpeg的c函數，這裏進行了註冊。終於分析完了，總結起來就是各類初始化，協議的、解碼器的、網絡的、回調上層的。
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