JavaCV 拉流存储到本地示例解析

import org.bytedeco.ffmpeg.global.avcodec;
import org.bytedeco.javacv.*;
public class LivePuller {
    public void pull(String rtmp, String outputVideoPath) {
        FFmpegFrameGrabber grabber = null;
        FFmpegFrameRecorder recorder = null;
        try {
            FFmpegLogCallback.set();
            boolean hasStream = false;
            grabber = new FFmpegFrameGrabber(rtmp);
            grabber.setOption("nobuffer", "1");
            // 采集流超时时间，停止推流后，grab() 大致会在 20 秒左右超时停止；值也不宜太小，否则可能有些音视频帧采集不到影响推流
            grabber.setOption("rw_timeout", "1000000");
            grabber.setVideoCodec(avcodec.AV_CODEC_ID_MPEG4);
            // setPixelFormat，可能会导致图片帧保存的是黑白照
//            grabber.setPixelFormat(avutil.AV_PIX_FMT_YUV420P);
            grabber.setFormat("flv");
            grabber.setAudioCodec(avcodec.AV_CODEC_ID_AAC);
            // 先执行代码后有直播流的情况下，grabber.start() 会抛出异常；因此循环start()，直到有流数据时成功
            while (!hasStream) {
                try {
                    grabber.start();
                    hasStream = true;
                } catch (Exception ignored) {
                } finally {
                    try {
                        Thread.sleep(100);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
            // 重置分辨率
            int imageWidth = grabber.getImageWidth();
            int imageHeight = grabber.getImageHeight();
            if (imageWidth > 1920 || imageHeight > 1080) {
                double wScale = imageWidth * 1.0 / 1920;
                double hScale = imageHeight * 1.0 / 1080;
                double scale = Math.max(wScale, hScale);
                grabber.setImageWidth((int) (imageWidth / scale));
                grabber.setImageHeight((int) (imageHeight / scale));
            }
            recorder = new FFmpegFrameRecorder(outputVideoPath, grabber.getImageWidth(), grabber.getImageHeight());
            recorder.setOption("nobuffer", "1");
            recorder.setAudioChannels(grabber.getAudioChannels());
            recorder.setFrameRate(grabber.getFrameRate());  // 保持和采集一样的帧率，避免音画不同步；
            recorder.setVideoQuality(0);    // 视频质量（清晰度）
            recorder.setAudioQuality(0);    // 音频质量
            // --------------------------- 非必须 ------------------------------
            // 当设置了下方的录制器的视频编码，需要再加上 setVideoBitrate 保证视频质量
            recorder.setVideoBitrate(grabber.getVideoBitrate());
            recorder.setVideoCodec(grabber.getVideoCodec());    // 指定为 mp4 录制时需要 avcodec.AV_CODEC_ID_MPEG4
//            // 当上面 grabber 没有设置 setPixelFormat，recorder.setPixelFormat 最好不要使用 grabber.getPixelFormat()；可能异常
//            recorder.setPixelFormat(grabber.getPixelFormat());
//            recorder.setFormat(grabber.getFormat());
//            recorder.setAudioCodec(grabber.getAudioCodec());
//            recorder.setSampleRate(grabber.getSampleRate());
            recorder.start();
            Frame frame;
            while ((frame = grabber.grab()) != null) {
                // 此处不能判断 frame.streamIndex 为 avutil.AVMEDIA_TYPE_VIDEO 或 avutil.AVMEDIA_TYPE_DATA；遇到过采集流时两个类型是反着的
                if (frame.image != null || frame.samples != null) {
                    // frame.image 是图像数据，frame.samples 是声音数据
                    recorder.record(frame);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (grabber != null) {
                try {
                    grabber.close();
                } catch (FrameGrabber.Exception e) {
                    e.printStackTrace();
                }
            }
            if (recorder != null) {
                try {
                    recorder.close();
                } catch (FrameRecorder.Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }
}