PHP调用摄像头进行实时视频编码：从输入到输出的实践

<?php
// 初始化
$ffi = FFI::cdef("
    typedef void * AVFormatContext;
    typedef void * AVCodecContext;
    typedef void * AVFrame;
    typedef void * AVPacket;
    typedef struct {
        int width;
        int height;
        int size;
        int format;
    } AVFrameInfo;
    
    AVFormatContext *avformat_alloc_context();
    int avformat_open_input(AVFormatContext **ps, const char *url, void *fmt, void *options);
    int avformat_find_stream_info(AVFormatContext *ic, void *options);
    void avformat_close_input(AVFormatContext **s);
    
    AVCodecContext *avcodec_alloc_context3(void *codec);
    void avcodec_close(AVCodecContext *avctx);
    void avcodec_free_context(AVCodecContext **avctx);
    
    AVFrame *av_frame_alloc();
    void av_frame_free(AVFrame **frame);
    
    AVPacket *av_packet_alloc();
    void av_packet_free(AVPacket **pkt);
    
    int av_read_frame(AVFormatContext *s, AVPacket *pkt);
    int avcodec_send_packet(AVCodecContext *avctx, AVPacket *avpkt);
    int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame);
    
    int av_image_get_buffer_size(int pix_fmt, int width, int height, int align);
    int av_image_alloc(uint8_t *pointers[4], int linesizes[4], int w, int h, int pix_fmt, int align);
    void av_freep(void *ptr);
    void av_image_fill_arrays(uint8_t *dst_data[4], int dst_linesize[4], const uint8_t *src,
                              int pix_fmt, int width, int height, int align);
    void av_image_copy(uint8_t *dst_data[4], int dst_linesize[4],
                       const uint8_t *src_data[4], const int src_linesize[4],
                       int pix_fmt, int width, int height);
    void av_image_copy_plane(uint8_t *dst, int dst_linesize, const uint8_t *src, int src_linesize, int bytewidth, int height);
    
    void av_init_packet(AVPacket *pkt);
", "libavformat.so.58");

// 打开摄像头
$formatContext = $ffi->avformat_alloc_context();
$source = "/dev/video0";
$ffi->avformat_open_input(FFI::addr($formatContext), $source, null, null);
$ffi->avformat_find_stream_info($formatContext, null);

// 查找视频流
$videoStreamIndex = -1;
for ($i = 0; $i < $formatContext->nb_streams; $i++) {
    if ($formatContext->streams[$i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
        $videoStreamIndex = $i;
        break;
    }
}

if ($videoStreamIndex == -1) {
    die("未找到视频流");
}

// 获取视频流信息
$videoCodecPar = $formatContext->streams[$videoStreamIndex]->codecpar;
$videoCodec = $ffi->avcodec_find_decoder($videoCodecPar->codec_id);
$codecContext = $ffi->avcodec_alloc_context3($videoCodec);
$videoFrame = $ffi->av_frame_alloc();
$packet = $ffi->av_packet_alloc();
$frameInfo = FFI::new("AVFrameInfo");

// 设置解码器上下文参数
$ffi->avcodec_parameters_to_context($codecContext, $videoCodecPar);
$ffi->avcodec_open2($codecContext, $videoCodec, null);

while ($ffi->av_read_frame($formatContext, $packet) >= 0) {
    // 解码视频帧
    if ($packet->stream_index == $videoStreamIndex) {
        $ffi->avcodec_send_packet($codecContext, $packet);
        while ($ffi->avcodec_receive_frame($codecContext, $videoFrame) >= 0) {
            // 获取视频帧信息
            $frameInfo->width = $videoFrame->width;
            $frameInfo->height = $videoFrame->height;
            $frameInfo->size = $ffi->av_image_get_buffer_size($videoFrame->format, $videoFrame->width, $videoFrame->height, 1);
            $frameInfo->format = $videoFrame->format;
            
            // 分配输出缓冲区
            $outBuffers = FFI::new("uint8_t[4]");
            $outLinesizes = FFI::new("int[4]");
            
            $ffi->av_image_alloc(FFI::addr($outBuffers), FFI::addr($outLinesizes), $frameInfo->width, $frameInfo->height, $frameInfo->format, 1);
            
            // 复制解码后的图像数据到输出缓冲区
            $ffi->av_image_copy($outBuffers, $outLinesizes, $videoFrame->data, $videoFrame->linesize, $frameInfo->format, $frameInfo->width, $frameInfo->height);
            
            // 输出图像数据，可以自行处理例如将图像数据发送给Web页面的Canvas元素
            // 这里只是简单地输出一帧的数据
            echo $outBuffers[0];
            
            // 释放输出缓冲区
            $ffi->av_freep($outBuffers);
        }
    }
    
    $ffi->av_packet_unref($packet);
}

// 释放资源
$ffi->av_frame_free(FFI::addr($videoFrame));
$ffi->avcodec_close($codecContext);
$ffi->avcodec_free_context($codecContext);
$ffi->avformat_close_input(FFI::addr($formatContext));

?>