学步园

1. Android4.0.1中默认定义了4个真正的Player,具体情况如下：

static sp<MediaPlayerBase> createPlayer(player_type playerType, void* cookie,
        notify_callback_f notifyFunc)
{
    sp<MediaPlayerBase> p;
    switch (playerType) {
        case SONIVOX_PLAYER:
            LOGV(" create MidiFile");
            p = new MidiFile();
            break;
        case STAGEFRIGHT_PLAYER:
            LOGV(" create StagefrightPlayer");
            p = new StagefrightPlayer;
            break;
        case NU_PLAYER:
            LOGV(" create NuPlayer");
            p = new NuPlayerDriver;
            break;
        case TEST_PLAYER:
            LOGV("Create Test Player stub");
            p = new TestPlayerStub();
            break;
        default:
            LOGE("Unknown player type: %d", playerType);
            return NULL;
    }
    if (p != NULL) {
        if (p->initCheck() == NO_ERROR) {
            p->setNotifyCallback(cookie, notifyFunc);
        } else {
            p.clear();
        }
    }
    if (p == NULL) {
        LOGE("Failed to create player object");
    }
    return p;
}

2. 每个Player的专长是什么呢？

以上言论以代码为证，获取player type的代码如下：

player_type getPlayerType(const char* url)
{
    if (TestPlayerStub::canBeUsed(url)) {
        return TEST_PLAYER;
    }

    if (!strncasecmp("http://", url, 7)
            || !strncasecmp("https://", url, 8)) {
        size_t len = strlen(url);
        if (len >= 5 && !strcasecmp(".m3u8", &url[len - 5])) {
            return NU_PLAYER;
        }

        if (strstr(url,"m3u8")) {
            return NU_PLAYER;
        }
    }

    // use MidiFile for MIDI extensions
    int lenURL = strlen(url);
    for (int i = 0; i < NELEM(FILE_EXTS); ++i) {
        int len = strlen(FILE_EXTS[i].extension);
        int start = lenURL - len;
        if (start > 0) {
            if (!strncasecmp(url + start, FILE_EXTS[i].extension, len)) {
                return FILE_EXTS[i].playertype;
            }
        }
    }

    return getDefaultPlayerType();
}

如果你想增加自己的player,以上两个函数都需要修改。

现在对整个媒体系统基本上有一个清晰的框架了，就突发奇想，到底在StagefrightPlayer如何增加自己的硬件解码呢? 很好奇，想一探究竟...