openmw-tes3mp/extern/ogre-ffmpeg-videoplayer/videostate.cpp

#include "videostate.hpp"

#ifndef __STDC_CONSTANT_MACROS
#define __STDC_CONSTANT_MACROS
#endif
#include <stdint.h>

// Has to be included *before* ffmpeg, due to a macro collision with ffmpeg (#define PixelFormat in avformat.h - grumble)
#include <OgreTextureManager.h>
#include <OgreHardwarePixelBuffer.h>
#include <OgreResourceGroupManager.h>
#include <OgreStringConverter.h>

extern "C"
{
    #include <libavcodec/avcodec.h>
    #include <libavformat/avformat.h>
    #include <libswscale/swscale.h>

    // From libavformat version 55.0.100 and onward the declaration of av_gettime() is
    // removed from libavformat/avformat.h and moved to libavutil/time.h
    // https://github.com/FFmpeg/FFmpeg/commit/06a83505992d5f49846c18507a6c3eb8a47c650e
    #if AV_VERSION_INT(55, 0, 100) <= AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
        LIBAVFORMAT_VERSION_MINOR, LIBAVFORMAT_VERSION_MICRO)
        #include <libavutil/time.h>
    #endif

    #include <libavutil/mathematics.h>

    #if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(55,28,1)
    #define av_frame_alloc  avcodec_alloc_frame
    #endif

}

static const char* flushString = "FLUSH";
struct FlushPacket : AVPacket
{
    FlushPacket()
        : AVPacket()
    {
        data = ( (uint8_t*)flushString);
    }
};

static FlushPacket flush_pkt;

#include "videoplayer.hpp"
#include "audiodecoder.hpp"
#include "audiofactory.hpp"

namespace
{
    const int MAX_AUDIOQ_SIZE = (5 * 16 * 1024);
    const int MAX_VIDEOQ_SIZE = (5 * 256 * 1024);
}

namespace Video
{

VideoState::VideoState()
    : format_ctx(NULL), av_sync_type(AV_SYNC_DEFAULT)
    , audio_st(NULL)
    , video_st(NULL), frame_last_pts(0.0)
    , video_clock(0.0), sws_context(NULL), rgbaFrame(NULL), pictq_size(0)
    , pictq_rindex(0), pictq_windex(0)
    , mQuit(false), mPaused(false)
    , mAudioFactory(NULL)
    , mSeekRequested(false)
    , mSeekPos(0)
    , mVideoEnded(false)
{
    mFlushPktData = flush_pkt.data;

    // Register all formats and codecs
    av_register_all();
}

VideoState::~VideoState()
{
    deinit();
}

void VideoState::setAudioFactory(MovieAudioFactory *factory)
{
    mAudioFactory = factory;
}


void PacketQueue::put(AVPacket *pkt)
{
    AVPacketList *pkt1;
    pkt1 = (AVPacketList*)av_malloc(sizeof(AVPacketList));
    if(!pkt1) throw std::bad_alloc();
    pkt1->pkt = *pkt;
    pkt1->next = NULL;

    if(pkt->data != flush_pkt.data && pkt1->pkt.destruct == NULL)
    {
        if(av_dup_packet(&pkt1->pkt) < 0)
        {
            av_free(pkt1);
            throw std::runtime_error("Failed to duplicate packet");
        }
        av_free_packet(pkt);
    }

    this->mutex.lock ();

    if(!last_pkt)
        this->first_pkt = pkt1;
    else
        this->last_pkt->next = pkt1;
    this->last_pkt = pkt1;
    this->nb_packets++;
    this->size += pkt1->pkt.size;
    this->cond.notify_one();

    this->mutex.unlock();
}

int PacketQueue::get(AVPacket *pkt, VideoState *is)
{
    boost::unique_lock<boost::mutex> lock(this->mutex);
    while(!is->mQuit)
    {
        AVPacketList *pkt1 = this->first_pkt;
        if(pkt1)
        {
            this->first_pkt = pkt1->next;
            if(!this->first_pkt)
                this->last_pkt = NULL;
            this->nb_packets--;
            this->size -= pkt1->pkt.size;

            *pkt = pkt1->pkt;
            av_free(pkt1);

            return 1;
        }

        if(this->flushing)
            break;
        this->cond.wait(lock);
    }

    return -1;
}

void PacketQueue::flush()
{
    this->flushing = true;
    this->cond.notify_one();
}

void PacketQueue::clear()
{
    AVPacketList *pkt, *pkt1;

    this->mutex.lock();
    for(pkt = this->first_pkt; pkt != NULL; pkt = pkt1)
    {
        pkt1 = pkt->next;
        if (pkt->pkt.data != flush_pkt.data)
            av_free_packet(&pkt->pkt);
        av_freep(&pkt);
    }
    this->last_pkt = NULL;
    this->first_pkt = NULL;
    this->nb_packets = 0;
    this->size = 0;
    this->mutex.unlock ();
}

int VideoState::OgreResource_Read(void *user_data, uint8_t *buf, int buf_size)
{
    Ogre::DataStreamPtr stream = static_cast<VideoState*>(user_data)->stream;
    try
    {
        return stream->read(buf, buf_size);
    }
    catch (std::exception& e)
    {
        return 0;
    }
}

int VideoState::OgreResource_Write(void *user_data, uint8_t *buf, int buf_size)
{
    Ogre::DataStreamPtr stream = static_cast<VideoState*>(user_data)->stream;
    try
    {
        return stream->write(buf, buf_size);
    }
    catch (std::exception& e)
    {
        return 0;
    }
}

int64_t VideoState::OgreResource_Seek(void *user_data, int64_t offset, int whence)
{
    Ogre::DataStreamPtr stream = static_cast<VideoState*>(user_data)->stream;

    whence &= ~AVSEEK_FORCE;
    if(whence == AVSEEK_SIZE)
        return stream->size();
    if(whence == SEEK_SET)
        stream->seek(offset);
    else if(whence == SEEK_CUR)
        stream->seek(stream->tell()+offset);
    else if(whence == SEEK_END)
        stream->seek(stream->size()+offset);
    else
        return -1;

    return stream->tell();
}

void VideoState::video_display(VideoPicture *vp)
{
    if((*this->video_st)->codec->width != 0 && (*this->video_st)->codec->height != 0)
    {
        if (mTexture.isNull())
        {
            static int i = 0;
            mTexture = Ogre::TextureManager::getSingleton().createManual(
                            "ffmpeg/VideoTexture" + Ogre::StringConverter::toString(++i),
                                    Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME,
                                    Ogre::TEX_TYPE_2D,
                                    (*this->video_st)->codec->width, (*this->video_st)->codec->height,
                                    0,
                                    Ogre::PF_BYTE_RGBA,
                                    Ogre::TU_DYNAMIC_WRITE_ONLY_DISCARDABLE);
        }
        Ogre::PixelBox pb((*this->video_st)->codec->width, (*this->video_st)->codec->height, 1, Ogre::PF_BYTE_RGBA, &vp->data[0]);
        Ogre::HardwarePixelBufferSharedPtr buffer = mTexture->getBuffer();
        buffer->blitFromMemory(pb);
    }
}

void VideoState::video_refresh()
{
    boost::mutex::scoped_lock lock(this->pictq_mutex);
    if(this->pictq_size == 0)
        return;

    if (this->av_sync_type == AV_SYNC_VIDEO_MASTER)
    {
        VideoPicture* vp = &this->pictq[this->pictq_rindex];
        this->video_display(vp);

        this->pictq_rindex = (pictq_rindex+1) % VIDEO_PICTURE_QUEUE_SIZE;
        this->frame_last_pts = vp->pts;
        this->pictq_size--;
        this->pictq_cond.notify_one();
    }
    else
    {
        const float threshold = 0.03f;
        if (this->pictq[pictq_rindex].pts > this->get_master_clock() + threshold)
            return; // not ready yet to show this picture

        // TODO: the conversion to RGBA is done in the decoding thread, so if a picture is skipped here, then it was
        // unnecessarily converted. But we may want to replace the conversion by a pixel shader anyway (see comment in queue_picture)
        int i=0;
        for (; i<this->pictq_size-1; ++i)
        {
            if (this->pictq[pictq_rindex].pts + threshold <= this->get_master_clock())
                this->pictq_rindex = (this->pictq_rindex+1) % VIDEO_PICTURE_QUEUE_SIZE; // not enough time to show this picture
            else
                break;
        }

        assert (this->pictq_rindex < VIDEO_PICTURE_QUEUE_SIZE);
        VideoPicture* vp = &this->pictq[this->pictq_rindex];

        this->video_display(vp);

        this->frame_last_pts = vp->pts;

        this->pictq_size -= i;
        // update queue for next picture
        this->pictq_size--;
        this->pictq_rindex = (this->pictq_rindex+1) % VIDEO_PICTURE_QUEUE_SIZE;
        this->pictq_cond.notify_one();
    }
}


int VideoState::queue_picture(AVFrame *pFrame, double pts)
{
    VideoPicture *vp;

    /* wait until we have a new pic */
    {
        boost::unique_lock<boost::mutex> lock(this->pictq_mutex);
        while(this->pictq_size >= VIDEO_PICTURE_QUEUE_SIZE && !this->mQuit)
            this->pictq_cond.timed_wait(lock, boost::posix_time::milliseconds(1));
    }
    if(this->mQuit)
        return -1;

    this->pictq_mutex.lock();

    // windex is set to 0 initially
    vp = &this->pictq[this->pictq_windex];

    // Convert the image into RGBA format for Ogre
    // TODO: we could do this in a pixel shader instead, if the source format
    // matches a commonly used format (ie YUV420P)
    if(this->sws_context == NULL)
    {
        int w = (*this->video_st)->codec->width;
        int h = (*this->video_st)->codec->height;
        this->sws_context = sws_getContext(w, h, (*this->video_st)->codec->pix_fmt,
                                           w, h, PIX_FMT_RGBA, SWS_BICUBIC,
                                           NULL, NULL, NULL);
        if(this->sws_context == NULL)
            throw std::runtime_error("Cannot initialize the conversion context!\n");
    }

    vp->pts = pts;
    vp->data.resize((*this->video_st)->codec->width * (*this->video_st)->codec->height * 4);

    uint8_t *dst = &vp->data[0];
    sws_scale(this->sws_context, pFrame->data, pFrame->linesize,
              0, (*this->video_st)->codec->height, &dst, this->rgbaFrame->linesize);

    // now we inform our display thread that we have a pic ready
    this->pictq_windex = (this->pictq_windex+1) % VIDEO_PICTURE_QUEUE_SIZE;
    this->pictq_size++;
    this->pictq_mutex.unlock();

    return 0;
}

double VideoState::synchronize_video(AVFrame *src_frame, double pts)
{
    double frame_delay;

    /* if we have pts, set video clock to it */
    if(pts != 0)
        this->video_clock = pts;
    else
        pts = this->video_clock;

    /* update the video clock */
    frame_delay = av_q2d((*this->video_st)->codec->time_base);

    /* if we are repeating a frame, adjust clock accordingly */
    frame_delay += src_frame->repeat_pict * (frame_delay * 0.5);
    this->video_clock += frame_delay;

    return pts;
}


/* These are called whenever we allocate a frame
 * buffer. We use this to store the global_pts in
 * a frame at the time it is allocated.
 */
static int64_t global_video_pkt_pts = AV_NOPTS_VALUE;
static int our_get_buffer(struct AVCodecContext *c, AVFrame *pic)
{
    int ret = avcodec_default_get_buffer(c, pic);
    int64_t *pts = (int64_t*)av_malloc(sizeof(int64_t));
    *pts = global_video_pkt_pts;
    pic->opaque = pts;
    return ret;
}
static void our_release_buffer(struct AVCodecContext *c, AVFrame *pic)
{
    if(pic) av_freep(&pic->opaque);
    avcodec_default_release_buffer(c, pic);
}


void VideoState::video_thread_loop(VideoState *self)
{
    AVPacket pkt1, *packet = &pkt1;
    int frameFinished;
    AVFrame *pFrame;

    pFrame = av_frame_alloc();

    self->rgbaFrame = av_frame_alloc();
    avpicture_alloc((AVPicture*)self->rgbaFrame, PIX_FMT_RGBA, (*self->video_st)->codec->width, (*self->video_st)->codec->height);

    while(self->videoq.get(packet, self) >= 0)
    {
        if(packet->data == flush_pkt.data)
        {
            avcodec_flush_buffers((*self->video_st)->codec);

            self->pictq_mutex.lock();
            self->pictq_size = 0;
            self->pictq_rindex = 0;
            self->pictq_windex = 0;
            self->pictq_mutex.unlock();

            self->frame_last_pts = packet->pts * av_q2d((*self->video_st)->time_base);
            global_video_pkt_pts = self->frame_last_pts;
            continue;
        }

        // Save global pts to be stored in pFrame
        global_video_pkt_pts = packet->pts;
        // Decode video frame
        if(avcodec_decode_video2((*self->video_st)->codec, pFrame, &frameFinished, packet) < 0)
            throw std::runtime_error("Error decoding video frame");

        double pts = 0;
        if(packet->dts != AV_NOPTS_VALUE)
            pts = packet->dts;
        else if(pFrame->opaque && *(int64_t*)pFrame->opaque != AV_NOPTS_VALUE)
            pts = *(int64_t*)pFrame->opaque;
        pts *= av_q2d((*self->video_st)->time_base);

        av_free_packet(packet);

        // Did we get a video frame?
        if(frameFinished)
        {
            pts = self->synchronize_video(pFrame, pts);
            if(self->queue_picture(pFrame, pts) < 0)
                break;
        }
    }

    av_free(pFrame);

    avpicture_free((AVPicture*)self->rgbaFrame);
    av_free(self->rgbaFrame);
}

void VideoState::decode_thread_loop(VideoState *self)
{
    AVFormatContext *pFormatCtx = self->format_ctx;
    AVPacket pkt1, *packet = &pkt1;

    try
    {
        if(!self->video_st && !self->audio_st)
            throw std::runtime_error("No streams to decode");

        // main decode loop
        while(!self->mQuit)
        {
            if(self->mSeekRequested)
            {
                uint64_t seek_target = self->mSeekPos;
                int streamIndex = -1;

                int videoStreamIndex = -1;;
                int audioStreamIndex = -1;
                if (self->video_st)
                    videoStreamIndex = self->video_st - self->format_ctx->streams;
                if (self->audio_st)
                    audioStreamIndex = self->audio_st - self->format_ctx->streams;

                if(videoStreamIndex >= 0)
                    streamIndex = videoStreamIndex;
                else if(audioStreamIndex >= 0)
                    streamIndex = audioStreamIndex;

                uint64_t timestamp = seek_target;

                // QtCreator's highlighter doesn't like AV_TIME_BASE_Q's {} initializer for some reason
                AVRational avTimeBaseQ = AVRational(); // = AV_TIME_BASE_Q;
                avTimeBaseQ.num = 1;
                avTimeBaseQ.den = AV_TIME_BASE;

                if(streamIndex >= 0)
                    timestamp = av_rescale_q(seek_target, avTimeBaseQ, self->format_ctx->streams[streamIndex]->time_base);

                // AVSEEK_FLAG_BACKWARD appears to be needed, otherwise ffmpeg may seek to a keyframe *after* the given time
                // we want to seek to any keyframe *before* the given time, so we can continue decoding as normal from there on
                if(av_seek_frame(self->format_ctx, streamIndex, timestamp, AVSEEK_FLAG_BACKWARD) < 0)
                    std::cerr << "Error seeking " << self->format_ctx->filename << std::endl;
                else
                {
                    // Clear the packet queues and put a special packet with the new clock time
                    if(audioStreamIndex >= 0)
                    {
                        self->audioq.clear();
                        flush_pkt.pts = av_rescale_q(seek_target, avTimeBaseQ,
                            self->format_ctx->streams[audioStreamIndex]->time_base);
                        self->audioq.put(&flush_pkt);
                    }
                    if(videoStreamIndex >= 0)
                    {
                        self->videoq.clear();
                        flush_pkt.pts = av_rescale_q(seek_target, avTimeBaseQ,
                            self->format_ctx->streams[videoStreamIndex]->time_base);
                        self->videoq.put(&flush_pkt);
                    }
                    self->pictq_mutex.lock();
                    self->pictq_size = 0;
                    self->pictq_rindex = 0;
                    self->pictq_windex = 0;
                    self->pictq_mutex.unlock();
                    self->mExternalClock.set(seek_target);
                }
                self->mSeekRequested = false;
            }


            if((self->audio_st && self->audioq.size > MAX_AUDIOQ_SIZE) ||
               (self->video_st && self->videoq.size > MAX_VIDEOQ_SIZE))
            {
                boost::this_thread::sleep(boost::posix_time::milliseconds(10));
                continue;
            }

            if(av_read_frame(pFormatCtx, packet) < 0)
            {
                if (self->audioq.nb_packets == 0 && self->videoq.nb_packets == 0 && self->pictq_size == 0)
                    self->mVideoEnded = true;
                continue;
            }
            else
                self->mVideoEnded = false;

            // Is this a packet from the video stream?
            if(self->video_st && packet->stream_index == self->video_st-pFormatCtx->streams)
                self->videoq.put(packet);
            else if(self->audio_st && packet->stream_index == self->audio_st-pFormatCtx->streams)
                self->audioq.put(packet);
            else
                av_free_packet(packet);
        }
    }
    catch(std::runtime_error& e) {
        std::cerr << "An error occured playing the video: " << e.what () << std::endl;
    }
    catch(Ogre::Exception& e) {
        std::cerr << "An error occured playing the video: " << e.getFullDescription () << std::endl;
    }

    self->mQuit = true;
}


bool VideoState::update()
{
    this->video_refresh();
    return !this->mVideoEnded;
}


int VideoState::stream_open(int stream_index, AVFormatContext *pFormatCtx)
{
    AVCodecContext *codecCtx;
    AVCodec *codec;

    if(stream_index < 0 || stream_index >= static_cast<int>(pFormatCtx->nb_streams))
        return -1;

    // Get a pointer to the codec context for the video stream
    codecCtx = pFormatCtx->streams[stream_index]->codec;
    codec = avcodec_find_decoder(codecCtx->codec_id);
    if(!codec || (avcodec_open2(codecCtx, codec, NULL) < 0))
    {
        fprintf(stderr, "Unsupported codec!\n");
        return -1;
    }

    switch(codecCtx->codec_type)
    {
    case AVMEDIA_TYPE_AUDIO:
        this->audio_st = pFormatCtx->streams + stream_index;

        if (!mAudioFactory)
        {
            std::cerr << "No audio factory registered, can not play audio stream" << std::endl;
            avcodec_close((*this->audio_st)->codec);
            this->audio_st = NULL;
            return -1;
        }

        mAudioDecoder = mAudioFactory->createDecoder(this);
        if (!mAudioDecoder.get())
        {
            std::cerr << "Failed to create audio decoder, can not play audio stream" << std::endl;
            avcodec_close((*this->audio_st)->codec);
            this->audio_st = NULL;
            return -1;
        }
        mAudioDecoder->setupFormat();
        break;

    case AVMEDIA_TYPE_VIDEO:
        this->video_st = pFormatCtx->streams + stream_index;

        codecCtx->get_buffer = our_get_buffer;
        codecCtx->release_buffer = our_release_buffer;
        this->video_thread = boost::thread(video_thread_loop, this);
        break;

    default:
        break;
    }

    return 0;
}

void VideoState::init(const std::string& resourceName)
{
    int video_index = -1;
    int audio_index = -1;
    unsigned int i;

    this->av_sync_type = AV_SYNC_DEFAULT;
    this->mQuit = false;

    this->stream = Ogre::ResourceGroupManager::getSingleton().openResource(resourceName);
    if(this->stream.isNull())
        throw std::runtime_error("Failed to open video resource");

    AVIOContext *ioCtx = avio_alloc_context(NULL, 0, 0, this, OgreResource_Read, OgreResource_Write, OgreResource_Seek);
    if(!ioCtx) throw std::runtime_error("Failed to allocate AVIOContext");

    this->format_ctx = avformat_alloc_context();
    if(this->format_ctx)
        this->format_ctx->pb = ioCtx;

    // Open video file
    ///
    /// format_ctx->pb->buffer must be freed by hand,
    /// if not, valgrind will show memleak, see:
    ///
    /// https://trac.ffmpeg.org/ticket/1357
    ///
    if(!this->format_ctx || avformat_open_input(&this->format_ctx, resourceName.c_str(), NULL, NULL))
    {
        if (this->format_ctx != NULL)
        {
          if (this->format_ctx->pb != NULL)
          {
              av_free(this->format_ctx->pb->buffer);
              this->format_ctx->pb->buffer = NULL;

              av_free(this->format_ctx->pb);
              this->format_ctx->pb = NULL;
          }
        }
        // "Note that a user-supplied AVFormatContext will be freed on failure."
        this->format_ctx = NULL;
        av_free(ioCtx);
        throw std::runtime_error("Failed to open video input");
    }

    // Retrieve stream information
    if(avformat_find_stream_info(this->format_ctx, NULL) < 0)
        throw std::runtime_error("Failed to retrieve stream information");

    // Dump information about file onto standard error
    av_dump_format(this->format_ctx, 0, resourceName.c_str(), 0);

    for(i = 0;i < this->format_ctx->nb_streams;i++)
    {
        if(this->format_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO && video_index < 0)
            video_index = i;
        if(this->format_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO && audio_index < 0)
            audio_index = i;
    }

    mExternalClock.set(0);

    if(audio_index >= 0)
        this->stream_open(audio_index, this->format_ctx);

    if(video_index >= 0)
    {
        this->stream_open(video_index, this->format_ctx);
    }


    this->parse_thread = boost::thread(decode_thread_loop, this);
}

void VideoState::deinit()
{
    this->mQuit = true;

    this->audioq.flush();
    this->videoq.flush();

    mAudioDecoder.reset();

    if (this->parse_thread.joinable())
        this->parse_thread.join();
    if (this->video_thread.joinable())
        this->video_thread.join();

    if(this->audio_st)
        avcodec_close((*this->audio_st)->codec);
    this->audio_st = NULL;
    if(this->video_st)
        avcodec_close((*this->video_st)->codec);
    this->video_st = NULL;

    if(this->sws_context)
        sws_freeContext(this->sws_context);
    this->sws_context = NULL;

    if(this->format_ctx)
    {
        ///
        /// format_ctx->pb->buffer must be freed by hand,
        /// if not, valgrind will show memleak, see:
        ///
        /// https://trac.ffmpeg.org/ticket/1357
        ///
        if (this->format_ctx->pb != NULL)
        {
            av_free(this->format_ctx->pb->buffer);
            this->format_ctx->pb->buffer = NULL;

            av_free(this->format_ctx->pb);
            this->format_ctx->pb = NULL;
        }
        avformat_close_input(&this->format_ctx);
    }

    if (!mTexture.isNull())
    {
        Ogre::TextureManager::getSingleton().remove(mTexture->getName());
        mTexture.setNull();
    }
}

double VideoState::get_external_clock()
{
    return mExternalClock.get() / 1000000.0;
}

double VideoState::get_master_clock()
{
    if(this->av_sync_type == AV_SYNC_VIDEO_MASTER)
        return this->get_video_clock();
    if(this->av_sync_type == AV_SYNC_AUDIO_MASTER)
        return this->get_audio_clock();
    return this->get_external_clock();
}

double VideoState::get_video_clock()
{
    return this->frame_last_pts;
}

double VideoState::get_audio_clock()
{
    if (!mAudioDecoder.get())
        return 0.0;
    return mAudioDecoder->getAudioClock();
}

void VideoState::setPaused(bool isPaused)
{
    this->mPaused = isPaused;
    mExternalClock.setPaused(isPaused);
}

void VideoState::seekTo(double time)
{
    time = std::max(0.0, time);
    time = std::min(getDuration(), time);
    mSeekPos = (uint64_t) (time * AV_TIME_BASE);
    mSeekRequested = true;
}

double VideoState::getDuration()
{
    return this->format_ctx->duration / 1000000.0;
}


ExternalClock::ExternalClock()
    : mTimeBase(av_gettime())
    , mPausedAt(0)
    , mPaused(false)
{
}

void ExternalClock::setPaused(bool paused)
{
    boost::mutex::scoped_lock lock(mMutex);
    if (mPaused == paused)
        return;
    if (paused)
    {
        mPausedAt = av_gettime() - mTimeBase;
    }
    else
        mTimeBase = av_gettime() - mPausedAt;
    mPaused = paused;
}

uint64_t ExternalClock::get()
{
    boost::mutex::scoped_lock lock(mMutex);
    if (mPaused)
        return mPausedAt;
    else
        return av_gettime() - mTimeBase;
}

void ExternalClock::set(uint64_t time)
{
    boost::mutex::scoped_lock lock(mMutex);
    mTimeBase = av_gettime() - time;
    mPausedAt = time;
}

}