录制视频

从音频那篇文章中可以知道，使用avfoundation 可以录制语音，但是事实上也是可以录制视频的，这篇文章会介绍一下如何操控录制视频

1.命令行录制

1.1查看avfoundation支持的设备

 ✘ songlin@feng-sl  ~/audio/YUV   master ±  ffmpeg -f avfoundation -list_devices true -i ''
ffmpeg version 4.3.2 Copyright (c) 2000-2021 the FFmpeg developers
  built with Apple clang version 12.0.0 (clang-1200.0.32.29)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.2_4 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
[AVFoundation indev @ 0x7f928cc04400] AVFoundation video devices:
[AVFoundation indev @ 0x7f928cc04400] [0] FaceTime HD Camera
[AVFoundation indev @ 0x7f928cc04400] [1] Capture screen 0
[AVFoundation indev @ 0x7f928cc04400] [2] Capture screen 1
[AVFoundation indev @ 0x7f928cc04400] AVFoundation audio devices:
[AVFoundation indev @ 0x7f928cc04400] [0] Built-in Microphone

从上面输出信息中可以看到0号设备就是Mac自带的摄像头

1.2 查看avfoundation支持的参数

 ✘ songlin@feng-sl  ~/audio/YUV   master ±  ffmpeg -h demuxer=avfoundation
ffmpeg version 4.3.2 Copyright (c) 2000-2021 the FFmpeg developers
  built with Apple clang version 12.0.0 (clang-1200.0.32.29)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.2_4 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Demuxer avfoundation [AVFoundation input device]:
AVFoundation indev AVOptions:
  -list_devices      <boolean>    .D........ list available devices (default false)
  -video_device_index <int>        .D........ select video device by index for devices with same name (starts at 0) (from -1 to INT_MAX) (default -1)
  -audio_device_index <int>        .D........ select audio device by index for devices with same name (starts at 0) (from -1 to INT_MAX) (default -1)
  -pixel_format      <pix_fmt>    .D........ set pixel format (default yuv420p)
  -framerate         <video_rate> .D........ set frame rate (default "ntsc")
  -video_size        <image_size> .D........ set video size
  -capture_cursor    <boolean>    .D........ capture the screen cursor (default false)
  -capture_mouse_clicks <boolean>    .D........ capture the screen mouse clicks (default false)
  -capture_raw_data  <boolean>    .D........ capture the raw data from device connection (default false)
  -drop_late_frames  <boolean>    .D........ drop frames that are available later than expected (default true)

• video_size: 分辨率
• pixel_format:像素格式(默认是yuv420p)
• framerate:幁率(每秒采集多少幁画面)，默认是ntsc，也就是3000/1001,约等于29.970030
• list_devices：true表示列出avfoundation支持的所有设备

1.3.开始录制

ffmpeg -f avfoundation -i 0 out.yuv

- 使用0号设备视频
ffmpeg -f avfoundation -i 0 out.yuv
ffmpeg version 4.3.2 Copyright (c) 2000-2021 the FFmpeg developers
  built with Apple clang version 12.0.0 (clang-1200.0.32.29)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.2_4 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
[avfoundation @ 0x7f98a080be00] Selected framerate (29.970030) is not supported by the device.
[avfoundation @ 0x7f98a080be00] Supported modes:
[avfoundation @ 0x7f98a080be00]   1280x720@[1.000000 30.000000]fps
    Last message repeated 2 times
[avfoundation @ 0x7f98a080be00]   640x480@[1.000000 30.000000]fps
    Last message repeated 2 times
[avfoundation @ 0x7f98a080be00]   320x240@[1.000000 30.000000]fps
    Last message repeated 2 times
0: Input/output error

• 错误信息：
• framerate (29.970030) is not supported by the device.并且告诉我们支持30fps的幁率

ffmpeg -f avfoundation -framerate 30 -i 0 video.yuv

✘ songlin@feng-sl  ~/audio/YUV   master ±  ffmpeg -f avfoundation -framerate 30 -i 0 video.yuv
ffmpeg version 4.3.2 Copyright (c) 2000-2021 the FFmpeg developers
  built with Apple clang version 12.0.0 (clang-1200.0.32.29)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.2_4 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
[avfoundation @ 0x7ffbd9009a00] Selected pixel format (yuv420p) is not supported by the input device.
[avfoundation @ 0x7ffbd9009a00] Supported pixel formats:
[avfoundation @ 0x7ffbd9009a00]   uyvy422
[avfoundation @ 0x7ffbd9009a00]   yuyv422
[avfoundation @ 0x7ffbd9009a00]   nv12
[avfoundation @ 0x7ffbd9009a00]   0rgb
[avfoundation @ 0x7ffbd9009a00]   bgr0
[avfoundation @ 0x7ffbd9009a00] Overriding selected pixel format to use uyvy422 instead.
Input #0, avfoundation, from '0':
  Duration: N/A, start: 98687.534833, bitrate: N/A
    Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 320x240, 29.97 tbr, 1000k tbn, 1000k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, rawvideo, to 'video.yuv':
  Metadata:
    encoder         : Lavf58.45.100
    Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 320x240, q=2-31, 36827 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc
    Metadata:
      encoder         : Lavc58.91.100 rawvideo
frame=  415 fps= 32 q=-0.0 size=   62208kB time=00:00:13.84 bitrate=36802.3kbits/s speed=1.05x

• 错误信息：
• Selected pixel format (yuv420p) is not supported by the input devic
• Supported pixel formats:uyvy422、yuyv422、nv12、0rgb、bgr0
• Overriding selected pixel format to use uyvy422 instead
  可以看出虽然报错，但是系统会帮我转换为可以录制的pixel format 执行下去，并且从输出信息里面还可以获取到的信息像素格式：uyvy422--------分辨率：20x240

1.4.播放视频

ffplay -video_size 320x240 -pixel_format uyvy422 -framerate  30 video.yuv

2.编程录制

添加依赖库

extern "C" {
#include <libavdevice/avdevice.h>
#include <libavformat/avformat.h>
#include <libavutil/avutil.h>
#include <libavutil/imgutils.h>
#include <libavcodec/avcodec.h>
}

定义宏

 #define FMT_NAME "avfoundation"
    #define DEVICE_NAME "0"
    #define FILENAME "/Users/songlin/audion/code_out.yuv

#define ERROR_BUF(ret) \
    char errbuf[1024]; \
    av_strerror(ret, errbuf, sizeof (errbuf));

Info.plist 权限申请

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>NSCameraUsageDescription</key>
        <string>使用摄像头采集您的帅气样子</string>
</dict>
</plist>

注册设备
如果没有注册设备，会爆出找不到avfoundation这个错误

// 初始化libavdevice并注册所有输入和输出设备
avdevice_register_all();

获取输入格式对象

// 获取输入格式对象
AVInputFormat *fmt = av_find_input_format(FMT_NAME);
if (!fmt) {
    qDebug() << "av_find_input_format error" << FMT_NAME;
    return;
}

打开输入设备

// 格式上下文
AVFormatContext *ctx = nullptr;
 
// 传递给输入设备的参数
AVDictionary *options = nullptr;
av_dict_set(&options, "video_size", "640x480", 0);
av_dict_set(&options, "pixel_format", "yuyv422", 0);
av_dict_set(&options, "framerate", "30", 0);
 
// 打开输入设备
int ret = avformat_open_input(&ctx, DEVICE_NAME, fmt, &options);
if (ret < 0) {
    ERROR_BUF(ret);
    qDebug() << "avformat_open_input error" << errbuf;
    return;
}

打开输出文件

// 打开文件
QFile file(FILENAME);
if (!file.open(QFile::WriteOnly)) {
    qDebug() << "file open error" << FILENAME;
 
    // 关闭输入设备
    avformat_close_input(&ctx);
    return;
}

采集视频数据

// 计算每一帧的大小
AVCodecParameters *params = ctx->streams[0]->codecpar;
int imageSize = av_image_get_buffer_size(
                    (AVPixelFormat) params->format,
                    params->width, params->height,
                    1);
 
// 数据包
AVPacket *pkt = av_packet_alloc();
while (!isInterruptionRequested()) {
    // 不断采集数据
    ret = av_read_frame(ctx, pkt);
 
    if (ret == 0) { // 读取成功
        // 将数据写入文件
        file.write((const char *) pkt->data, imageSize);
        /*
         这里要使用imageSize，而不是pkt->size。
         pkt->size有可能比imageSize大（比如在Mac平台），
         使用pkt->size会导致写入一些多余数据到YUV文件中，
         进而导致YUV内容无法正常播放
        */
 
        // 释放资源
        av_packet_unref(pkt);
    } else if (ret == AVERROR(EAGAIN)) { // 资源临时不可用
        continue;
    } else { // 其他错误
        ERROR_BUF(ret);
        qDebug() << "av_read_frame error" << errbuf;
        break;
    }
}

释放资源

// 释放资源
av_packet_free(&pkt);
 
// 关闭文件
file.close();
 
// 关闭设备
avformat_close_input(&ctx);

测试录制视频

 ffplay -video_size 640x480 -pixel_format yuyv422 -framerate  30 code_out.yuv