关于C#:从RTP流解码h264帧

 2021-04-09 

Decoding h264 frames from RTP stream

我正在使用live555和ffmpeg库从服务器获取和解码RTP H264流; ffmpeg使用基线配置文件和

对视频流进行了编码

1
x264_param_default_preset(m_params,"veryfast","zerolatency")

我阅读了本主题,并在从网络接收到的每一帧中添加了SPS和PPS数据;

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
void ClientSink::NewFrameHandler(unsigned frameSize, unsigned numTruncatedBytes,
    timeval presentationTime, unsigned durationInMicroseconds)
{
     ...
EncodedFrame tmp;
    tmp.m_frame = std::vector<unsigned char>(m_tempBuffer.data(), m_tempBuffer.data() + frameSize);
    tmp.m_duration = durationInMicroseconds;
    tmp.m_pts = presentationTime;

    //Add SPS and PPS data into the frame; TODO: some devices may send SPS and PPs data already into frame;
    tmp.m_frame.insert(tmp.m_frame.begin(), m_spsPpsData.cbegin(), m_spsPpsData.cend());

    emit newEncodedFrame( SharedEncodedFrame(tmp) );
    m_frameCounter++;

    this->continuePlaying();
}

我在解码器中收到的这些帧。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
bool H264Decoder::decodeFrame(SharedEncodedFrame orig_frame)
{
...
while(m_packet.size > 0)
    {
        int got_picture;
        int len = avcodec_decode_video2(m_decoderContext, m_picture, &got_picture, &m_packet);
        if (len < 0)
        {
            emit criticalError(QString("Decoding error"));
            return false;
        }
        if (got_picture)
        {
            std::vector<unsigned char> result;
            this->storePicture(result);

            if ( m_picture->format == AVPixelFormat::AV_PIX_FMT_YUV420P )
            {
                //QImage img = QImage(result.data(), m_picture->width, m_picture->height, QImage::Format_RGB888);
                Frame_t result_rgb;
                if (!convert_yuv420p_to_rgb32(result, m_picture->width, m_picture->height, result_rgb))
                {
                    emit criticalError( QString("Failed to convert YUV420p image into rgb32; can't create QImage!"));
                    return false;
                }
                unsigned char* copy_img = new unsigned char[result_rgb.size()];
//this needed because QImage shared buffer, which used, and it will crash, if i use this qimage after result_rgb deleting
                std::copy(result_rgb.cbegin(), result_rgb.cend(), copy_img);
                QImage img = QImage(copy_img, m_picture->width, m_picture->height, QImage::Format_RGB32,
                [](void* array)
                {
                    delete[] array;
                }, copy_img);
                img.save(QString("123.bmp"));
                emit newDecodedFrame(img);
            }

avcodec_decode_video2解码帧没有任何错误消息,但是将其转换后(从yuv420p转换为rgb32)是无效的。此链接上可用图像的示例

您有什么想法我做错了吗?


我怀疑错误是在convert_yuv420p_to_rgb32()代码中。试试这个:

1
2
3
4
5
6
7
8
9
10
11
12
static SwsContext *m_swsCtx = NULL;
QImage frame =  QImage ( m_picture->width, m_picture->height,
                         QImage::Format_RGB32 );
m_swsCtx = sws_getCachedContext ( m_swsCtx, m_picture->width,
                                  m_picture->height, PIX_FMT_YUV420P,
                                  m_picture->width, m_picture->height,
                                  AV_PIX_FMT_RGB32, SWS_BICUBIC,
                                  NULL, NULL, NULL );
uint8_t *dstSlice[] = { frame.bits() };
int dstStride = frame.width() * 4;
sws_scale ( m_swsCtx, &m_picture.data, &m_picture.linesize,
            0, m_picture->height, dstSlice, &dstStride );

如果尚未包含/链接swscale,则需要包含/链接。

注意:您不需要每帧都使用SPS / PPS(在关键帧上就足够了)。但这也没有伤害。


好的。这是我的简单示例,它对从liveMedia库接收的H264流进行解码。它可以解码不仅在帧边界被截断的帧。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
   class H264Decoder : public AbstractDecoder
    {
        Q_OBJECT
    public:
        H264Decoder( QObject* parent = nullptr );
        virtual ~H264Decoder();

    public slots:

        virtual bool decodeFrame(SharedEncodedFrame orig_frame) override;

    signals:
        //sended when we have new decoded frame
        void newDecodedFrame( QImage img );

    protected:
        void storePicture(std::vector<unsigned char>& res);

        AVCodec* m_decoder;
        AVCodecContext* m_decoderContext;
        int m_got_picture;
        AVFrame* m_picture;
        AVPacket m_packet;
    };

这是实现:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
#include"H264Decoder.hpp"
#include"ImgConverting.hpp"
#include <QPixmap>
extern"C"
{
#include <libswscale/swscale.h>
}

using namespace std;

H264Decoder::H264Decoder( QObject *parent)
    : AbstractDecoder(parent), m_decoder(nullptr), m_decoderContext(nullptr),
      m_got_picture(0), m_picture(nullptr)
{
    avcodec_register_all();
    av_init_packet(&m_packet);
    m_decoder = avcodec_find_decoder(CODEC_ID_H264);
    if (!m_decoder)
    {
        QString str = QString("Can't find H264 decoder!");
        emit criticalError(str);
    }
    m_decoderContext = avcodec_alloc_context3(m_decoder);

    if (m_decoder->capabilities & CODEC_CAP_TRUNCATED)
        m_decoderContext->flags |= CODEC_FLAG_TRUNCATED;


    //we can receive truncated frames
    m_decoderContext->flags2 |= CODEC_FLAG2_CHUNKS;
    m_decoderContext->thread_count = 4;//TODO: random value. May be changing can make decoding faster

    AVDictionary* dictionary = nullptr;
    if (avcodec_open2(m_decoderContext, m_decoder, &dictionary) < 0)
    {
        QString str = QString("Failed to open decoder!");
        emit criticalError(str);
    }
    qDebug() <<"H264 Decoder successfully opened";
    m_picture = avcodec_alloc_frame();
}

H264Decoder::~H264Decoder()
{
    qDebug() <<"ACHTUNG!!! H264Decoder deleted!!!\
\
\
\
"
;
    if (m_decoderContext)
    {
        avcodec_close(m_decoderContext);
        delete m_decoderContext;
    }
}


bool H264Decoder::decodeFrame(SharedEncodedFrame orig_frame)
{
    Frame_t enc_frame;
    orig_frame >> enc_frame;
    m_packet.size = enc_frame.size();
    m_packet.data = enc_frame.data();

    qDebug() <<"H264Decoder: received encoded frame with framesize" << enc_frame.size();

    while(m_packet.size > 0)
    {
        int got_picture;
        int len = avcodec_decode_video2(m_decoderContext, m_picture, &got_picture, &m_packet);
        if (len < 0)
        {
            QString err("Decoding error");
            qDebug() << err;
            return false;
        }
        if (got_picture)
        {
            qDebug() <<"H264Decoder: frame decoded!";
            std::vector<unsigned char> result;
            this->storePicture(result);

            if ( m_picture->format == PIX_FMT_YUV420P )
            {
                static SwsContext *m_swsCtx = NULL;
                QImage frame_img = QImage(m_picture->width, m_picture->height, QImage::Format_RGB888);
                m_swsCtx = sws_getCachedContext ( m_swsCtx, m_picture->width,
                    m_picture->height, PIX_FMT_YUV420P,
                    m_picture->width, m_picture->height,
                    PIX_FMT_RGB24, SWS_GAUSS,
                    NULL, NULL, NULL );
                uint8_t *dstSlice[] = { frame_img.bits() };
                int dstStride = frame_img.width() * 3;
                if (sws_scale ( m_swsCtx, m_picture->data, m_picture->linesize,
                    0, m_picture->height, dstSlice, &dstStride ) != m_picture->height )
                {
                    qDebug() <<"PIZDETS!!!";
                    exit(-5);
                }
                qDebug() <<"New decoded image!";
                emit newDecodedFrame(frame_img);
            }
            else if (m_picture->format == PIX_FMT_RGB32)
            {
                QImage img = QImage(result.data(), m_picture->width, m_picture->height, QImage::Format_RGB32);
                qDebug() <<"New decoded image!";
                emit newDecodedFrame(img);
            }
            else if (m_picture->format == PIX_FMT_RGB24)
            {
                QImage img = QImage(result.data(), m_picture->width, m_picture->height, QImage::Format_RGB888);
                qDebug() <<"New decoded image!";
                emit newDecodedFrame(img);
            }
            else
            {
                QString err = QString("Unsupported pixel format! Can't create QImage!");
                qDebug() << err;
                emit criticalError( err );
                return false;
            }
        }
        m_packet.size -= len;
        m_packet.data += len;
    }

    return true;
}

void H264Decoder::storePicture(std::vector<unsigned char>& res)
{
    for (size_t i = 0; i < AV_NUM_DATA_POINTERS; i++)
    {
        std::copy(m_picture->data[i], m_picture->data[i] +
            m_picture->linesize[i]*m_picture->height, std::back_inserter(res));
    }
}

我将newDecodedFrame发送到GUI线程,该QImage将在某个小部件处绘制。

P.S:此评论很长才能发布为评论的评论