我使用FFmpegFrameRecorder从我的网络摄像头获取视频输入并将其记录到视频文件中。问题是，我正在使用我找到的几个不同的演示源代码构建我的应用程序，并且我使用了一些属性，其中一些对我来说并不完全清楚。
FFmpegFrameRecorder recorder = new FFmpegFrameRecorder(FILENAME, grabber.getImageWidth(),grabber.getImageHeight());
recorder.setVideoCodec(13);
recorder.setFormat("mp4");
recorder.setPixelFormat(avutil.PIX_FMT_YUV420P);
recorder.setFrameRate(30);
recorder.setVideoBitrate(10 * 1024 * 1024);
recorder.start();
- setVideoCodec(13) -这个
(13)的含义是什么我怎么能理解实际的编解码器站在任何数字背后? - setPixelFormat -只是得到这个，不知道它在做什么
- setFrameRate(30) -我认为这应该是非常清楚的，但仍然是什么背后的逻辑帧率我们选择(是不是越高越好?)
- setVideoBitrate(10*1024*1024) -再次几乎不知道这是做什么和数字背后的逻辑是什么?
最后我想提一下我录制这样的视频时遇到的最后一个问题。如果视频的实际长度是20秒。当我播放从程序创建的视频文件时，它运行得快得多。我不知道它是否比应该快2倍，但一般来说，如果我录制一个20秒的视频，那么它会播放大约10秒。可能导致这种情况的原因是什么?我该如何解决?
视频编解码器可以从avcodec.h/avcodec.java中找到的列表中选择(正如您所看到的，数字13使我们获得MPEG4，还有其他，但FFmpeg没有为所有这些编码器):
AV_CODEC_ID_MPEG1VIDEO = 1,
/** preferred ID for MPEG-1/2 video decoding */
AV_CODEC_ID_MPEG2VIDEO = 2,
AV_CODEC_ID_MPEG2VIDEO_XVMC = 3,
AV_CODEC_ID_H261 = 4,
AV_CODEC_ID_H263 = 5,
AV_CODEC_ID_RV10 = 6,
AV_CODEC_ID_RV20 = 7,
AV_CODEC_ID_MJPEG = 8,
AV_CODEC_ID_MJPEGB = 9,
AV_CODEC_ID_LJPEG = 10,
AV_CODEC_ID_SP5X = 11,
AV_CODEC_ID_JPEGLS = 12,
AV_CODEC_ID_MPEG4 = 13,
AV_CODEC_ID_RAWVIDEO = 14,
AV_CODEC_ID_MSMPEG4V1 = 15,
AV_CODEC_ID_MSMPEG4V2 = 16,
AV_CODEC_ID_MSMPEG4V3 = 17,
AV_CODEC_ID_WMV1 = 18,
AV_CODEC_ID_WMV2 = 19,
AV_CODEC_ID_H263P = 20,
AV_CODEC_ID_H263I = 21,
AV_CODEC_ID_FLV1 = 22,
AV_CODEC_ID_SVQ1 = 23,
AV_CODEC_ID_SVQ3 = 24,
AV_CODEC_ID_DVVIDEO = 25,
AV_CODEC_ID_HUFFYUV = 26,
AV_CODEC_ID_CYUV = 27,
AV_CODEC_ID_H264 = 28,
AV_CODEC_ID_INDEO3 = 29,
AV_CODEC_ID_VP3 = 30,
AV_CODEC_ID_THEORA = 31,
AV_CODEC_ID_ASV1 = 32,
AV_CODEC_ID_ASV2 = 33,
AV_CODEC_ID_FFV1 = 34,
AV_CODEC_ID_4XM = 35,
AV_CODEC_ID_VCR1 = 36,
AV_CODEC_ID_CLJR = 37,
AV_CODEC_ID_MDEC = 38,
AV_CODEC_ID_ROQ = 39,
AV_CODEC_ID_INTERPLAY_VIDEO = 40,
AV_CODEC_ID_XAN_WC3 = 41,
AV_CODEC_ID_XAN_WC4 = 42,
AV_CODEC_ID_RPZA = 43,
AV_CODEC_ID_CINEPAK = 44,
AV_CODEC_ID_WS_VQA = 45,
AV_CODEC_ID_MSRLE = 46,
AV_CODEC_ID_MSVIDEO1 = 47,
AV_CODEC_ID_IDCIN = 48,
AV_CODEC_ID_8BPS = 49,
AV_CODEC_ID_SMC = 50,
AV_CODEC_ID_FLIC = 51,
AV_CODEC_ID_TRUEMOTION1 = 52,
AV_CODEC_ID_VMDVIDEO = 53,
AV_CODEC_ID_MSZH = 54,
AV_CODEC_ID_ZLIB = 55,
AV_CODEC_ID_QTRLE = 56,
AV_CODEC_ID_TSCC = 57,
AV_CODEC_ID_ULTI = 58,
AV_CODEC_ID_QDRAW = 59,
AV_CODEC_ID_VIXL = 60,
AV_CODEC_ID_QPEG = 61,
AV_CODEC_ID_PNG = 62,
AV_CODEC_ID_PPM = 63,
AV_CODEC_ID_PBM = 64,
AV_CODEC_ID_PGM = 65,
AV_CODEC_ID_PGMYUV = 66,
AV_CODEC_ID_PAM = 67,
AV_CODEC_ID_FFVHUFF = 68,
AV_CODEC_ID_RV30 = 69,
AV_CODEC_ID_RV40 = 70,
AV_CODEC_ID_VC1 = 71,
AV_CODEC_ID_WMV3 = 72,
AV_CODEC_ID_LOCO = 73,
AV_CODEC_ID_WNV1 = 74,
AV_CODEC_ID_AASC = 75,
AV_CODEC_ID_INDEO2 = 76,
AV_CODEC_ID_FRAPS = 77,
AV_CODEC_ID_TRUEMOTION2 = 78,
AV_CODEC_ID_BMP = 79,
AV_CODEC_ID_CSCD = 80,
AV_CODEC_ID_MMVIDEO = 81,
AV_CODEC_ID_ZMBV = 82,
AV_CODEC_ID_AVS = 83,
AV_CODEC_ID_SMACKVIDEO = 84,
AV_CODEC_ID_NUV = 85,
AV_CODEC_ID_KMVC = 86,
AV_CODEC_ID_FLASHSV = 87,
AV_CODEC_ID_CAVS = 88,
AV_CODEC_ID_JPEG2000 = 89,
AV_CODEC_ID_VMNC = 90,
AV_CODEC_ID_VP5 = 91,
AV_CODEC_ID_VP6 = 92,
AV_CODEC_ID_VP6F = 93,
AV_CODEC_ID_TARGA = 94,
AV_CODEC_ID_DSICINVIDEO = 95,
AV_CODEC_ID_TIERTEXSEQVIDEO = 96,
AV_CODEC_ID_TIFF = 97,
AV_CODEC_ID_GIF = 98,
AV_CODEC_ID_DXA = 99,
AV_CODEC_ID_DNXHD = 100,
AV_CODEC_ID_THP = 101,
AV_CODEC_ID_SGI = 102,
AV_CODEC_ID_C93 = 103,
AV_CODEC_ID_BETHSOFTVID = 104,
AV_CODEC_ID_PTX = 105,
AV_CODEC_ID_TXD = 106,
AV_CODEC_ID_VP6A = 107,
AV_CODEC_ID_AMV = 108,
AV_CODEC_ID_VB = 109,
AV_CODEC_ID_PCX = 110,
AV_CODEC_ID_SUNRAST = 111,
AV_CODEC_ID_INDEO4 = 112,
AV_CODEC_ID_INDEO5 = 113,
AV_CODEC_ID_MIMIC = 114,
AV_CODEC_ID_RL2 = 115,
AV_CODEC_ID_ESCAPE124 = 116,
AV_CODEC_ID_DIRAC = 117,
AV_CODEC_ID_BFI = 118,
AV_CODEC_ID_CMV = 119,
AV_CODEC_ID_MOTIONPIXELS = 120,
AV_CODEC_ID_TGV = 121,
AV_CODEC_ID_TGQ = 122,
AV_CODEC_ID_TQI = 123,
AV_CODEC_ID_AURA = 124,
AV_CODEC_ID_AURA2 = 125,
AV_CODEC_ID_V210X = 126,
AV_CODEC_ID_TMV = 127,
AV_CODEC_ID_V210 = 128,
AV_CODEC_ID_DPX = 129,
AV_CODEC_ID_MAD = 130,
AV_CODEC_ID_FRWU = 131,
AV_CODEC_ID_FLASHSV2 = 132,
AV_CODEC_ID_CDGRAPHICS = 133,
AV_CODEC_ID_R210 = 134,
AV_CODEC_ID_ANM = 135,
AV_CODEC_ID_BINKVIDEO = 136,
AV_CODEC_ID_IFF_ILBM = 137,
AV_CODEC_ID_IFF_BYTERUN1 = 138,
AV_CODEC_ID_KGV1 = 139,
AV_CODEC_ID_YOP = 140,
AV_CODEC_ID_VP8 = 141,
AV_CODEC_ID_PICTOR = 142,
AV_CODEC_ID_ANSI = 143,
AV_CODEC_ID_A64_MULTI = 144,
AV_CODEC_ID_A64_MULTI5 = 145,
AV_CODEC_ID_R10K = 146,
AV_CODEC_ID_MXPEG = 147,
AV_CODEC_ID_LAGARITH = 148,
AV_CODEC_ID_PRORES = 149,
AV_CODEC_ID_JV = 150,
AV_CODEC_ID_DFA = 151,
AV_CODEC_ID_WMV3IMAGE = 152,
AV_CODEC_ID_VC1IMAGE = 153,
AV_CODEC_ID_UTVIDEO = 154,
AV_CODEC_ID_BMV_VIDEO = 155,
AV_CODEC_ID_VBLE = 156,
AV_CODEC_ID_DXTORY = 157,
AV_CODEC_ID_V410 = 158,
AV_CODEC_ID_XWD = 159,
AV_CODEC_ID_CDXL = 160,
AV_CODEC_ID_XBM = 161,
AV_CODEC_ID_ZEROCODEC = 162,
AV_CODEC_ID_MSS1 = 163,
AV_CODEC_ID_MSA1 = 164,
AV_CODEC_ID_TSCC2 = 165,
AV_CODEC_ID_MTS2 = 166,
AV_CODEC_ID_CLLC = 167,
AV_CODEC_ID_MSS2 = 168,
AV_CODEC_ID_VP9 = 169,
AV_CODEC_ID_AIC = 170,
// etc
PixelFormat可以在pixfmt.h/avutil.java中从这个列表中选择，但是每个编解码器只支持其中的几个(其中大多数至少支持AV_PIX_FMT_YUV420P):
/** planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples) */
AV_PIX_FMT_YUV420P = 0,
/** packed YUV 4:2:2, 16bpp, Y0 Cb Y1 Cr */
AV_PIX_FMT_YUYV422 = 1,
/** packed RGB 8:8:8, 24bpp, RGBRGB... */
AV_PIX_FMT_RGB24 = 2,
/** packed RGB 8:8:8, 24bpp, BGRBGR... */
AV_PIX_FMT_BGR24 = 3,
/** planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples) */
AV_PIX_FMT_YUV422P = 4,
/** planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples) */
AV_PIX_FMT_YUV444P = 5,
/** planar YUV 4:1:0, 9bpp, (1 Cr & Cb sample per 4x4 Y samples) */
AV_PIX_FMT_YUV410P = 6,
/** planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples) */
AV_PIX_FMT_YUV411P = 7,
/** Y , 8bpp */
AV_PIX_FMT_GRAY8 = 8,
/** Y , 1bpp, 0 is white, 1 is black, in each byte pixels are ordered from the msb to the lsb */
AV_PIX_FMT_MONOWHITE = 9,
/** Y , 1bpp, 0 is black, 1 is white, in each byte pixels are ordered from the msb to the lsb */
AV_PIX_FMT_MONOBLACK = 10,
/** 8 bit with PIX_FMT_RGB32 palette */
AV_PIX_FMT_PAL8 = 11,
/** planar YUV 4:2:0, 12bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV420P and setting color_range */
AV_PIX_FMT_YUVJ420P = 12,
/** planar YUV 4:2:2, 16bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV422P and setting color_range */
AV_PIX_FMT_YUVJ422P = 13,
/** planar YUV 4:4:4, 24bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV444P and setting color_range */
AV_PIX_FMT_YUVJ444P = 14,
/** XVideo Motion Acceleration via common packet passing */
AV_PIX_FMT_XVMC_MPEG2_MC = 15,
AV_PIX_FMT_XVMC_MPEG2_IDCT = 16;
/** packed YUV 4:2:2, 16bpp, Cb Y0 Cr Y1 */
AV_PIX_FMT_UYVY422 = 17,
/** packed YUV 4:1:1, 12bpp, Cb Y0 Y1 Cr Y2 Y3 */
AV_PIX_FMT_UYYVYY411 = 18,
/** packed RGB 3:3:2, 8bpp, (msb)2B 3G 3R(lsb) */
AV_PIX_FMT_BGR8 = 19,
/** packed RGB 1:2:1 bitstream, 4bpp, (msb)1B 2G 1R(lsb), a byte contains two pixels, the first pixel in the byte is the one composed by the 4 msb bits */
AV_PIX_FMT_BGR4 = 20,
/** packed RGB 1:2:1, 8bpp, (msb)1B 2G 1R(lsb) */
AV_PIX_FMT_BGR4_BYTE = 21,
/** packed RGB 3:3:2, 8bpp, (msb)2R 3G 3B(lsb) */
AV_PIX_FMT_RGB8 = 22,
/** packed RGB 1:2:1 bitstream, 4bpp, (msb)1R 2G 1B(lsb), a byte contains two pixels, the first pixel in the byte is the one composed by the 4 msb bits */
AV_PIX_FMT_RGB4 = 23,
/** packed RGB 1:2:1, 8bpp, (msb)1R 2G 1B(lsb) */
AV_PIX_FMT_RGB4_BYTE = 24,
/** planar YUV 4:2:0, 12bpp, 1 plane for Y and 1 plane for the UV components, which are interleaved (first byte U and the following byte V) */
AV_PIX_FMT_NV12 = 25,
/** as above, but U and V bytes are swapped */
AV_PIX_FMT_NV21 = 26,
/** packed ARGB 8:8:8:8, 32bpp, ARGBARGB... */
AV_PIX_FMT_ARGB = 27,
/** packed RGBA 8:8:8:8, 32bpp, RGBARGBA... */
AV_PIX_FMT_RGBA = 28,
/** packed ABGR 8:8:8:8, 32bpp, ABGRABGR... */
AV_PIX_FMT_ABGR = 29,
/** packed BGRA 8:8:8:8, 32bpp, BGRABGRA... */
AV_PIX_FMT_BGRA = 30,
/** Y , 16bpp, big-endian */
AV_PIX_FMT_GRAY16BE = 31,
/** Y , 16bpp, little-endian */
AV_PIX_FMT_GRAY16LE = 32,
/** planar YUV 4:4:0 (1 Cr & Cb sample per 1x2 Y samples) */
AV_PIX_FMT_YUV440P = 33,
/** planar YUV 4:4:0 full scale (JPEG), deprecated in favor of PIX_FMT_YUV440P and setting color_range */
AV_PIX_FMT_YUVJ440P = 34,
/** planar YUV 4:2:0, 20bpp, (1 Cr & Cb sample per 2x2 Y & A samples) */
AV_PIX_FMT_YUVA420P = 35,
/** H.264 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers */
AV_PIX_FMT_VDPAU_H264 = 36,
/** MPEG-1 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers */
AV_PIX_FMT_VDPAU_MPEG1 = 37,
/** MPEG-2 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers */
AV_PIX_FMT_VDPAU_MPEG2 = 38,
/** WMV3 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers */
AV_PIX_FMT_VDPAU_WMV3 = 39,
/** VC-1 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers */
AV_PIX_FMT_VDPAU_VC1 = 40,
/** packed RGB 16:16:16, 48bpp, 16R, 16G, 16B, the 2-byte value for each R/G/B component is stored as big-endian */
AV_PIX_FMT_RGB48BE = 41,
/** packed RGB 16:16:16, 48bpp, 16R, 16G, 16B, the 2-byte value for each R/G/B component is stored as little-endian */
AV_PIX_FMT_RGB48LE = 42,
/** packed RGB 5:6:5, 16bpp, (msb) 5R 6G 5B(lsb), big-endian */
AV_PIX_FMT_RGB565BE = 43,
/** packed RGB 5:6:5, 16bpp, (msb) 5R 6G 5B(lsb), little-endian */
AV_PIX_FMT_RGB565LE = 44,
/** packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), big-endian, most significant bit to 0 */
AV_PIX_FMT_RGB555BE = 45,
/** packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), little-endian, most significant bit to 0 */
AV_PIX_FMT_RGB555LE = 46,
/** packed BGR 5:6:5, 16bpp, (msb) 5B 6G 5R(lsb), big-endian */
AV_PIX_FMT_BGR565BE = 47,
/** packed BGR 5:6:5, 16bpp, (msb) 5B 6G 5R(lsb), little-endian */
AV_PIX_FMT_BGR565LE = 48,
/** packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), big-endian, most significant bit to 1 */
AV_PIX_FMT_BGR555BE = 49,
/** packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), little-endian, most significant bit to 1 */
AV_PIX_FMT_BGR555LE = 50,
/** HW acceleration through VA API at motion compensation entry-point, Picture.data[3] contains a vaapi_render_state struct which contains macroblocks as well as various fields extracted from headers */
AV_PIX_FMT_VAAPI_MOCO = 51,
/** HW acceleration through VA API at IDCT entry-point, Picture.data[3] contains a vaapi_render_state struct which contains fields extracted from headers */
AV_PIX_FMT_VAAPI_IDCT = 52,
/** HW decoding through VA API, Picture.data[3] contains a vaapi_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers */
AV_PIX_FMT_VAAPI_VLD = 53,
/** planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian */
AV_PIX_FMT_YUV420P16LE = 54,
/** planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian */
AV_PIX_FMT_YUV420P16BE = 55,
/** planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian */
AV_PIX_FMT_YUV422P16LE = 56,
/** planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian */
AV_PIX_FMT_YUV422P16BE = 57,
/** planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian */
AV_PIX_FMT_YUV444P16LE = 58,
/** planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian */
AV_PIX_FMT_YUV444P16BE = 59,
/** MPEG4 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers */
AV_PIX_FMT_VDPAU_MPEG4 = 60,
/** HW decoding through DXVA2, Picture.data[3] contains a LPDIRECT3DSURFACE9 pointer */
AV_PIX_FMT_DXVA2_VLD = 61,
/** packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), little-endian, most significant bits to 0 */
AV_PIX_FMT_RGB444LE = 62,
/** packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), big-endian, most significant bits to 0 */
AV_PIX_FMT_RGB444BE = 63,
/** packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), little-endian, most significant bits to 1 */
AV_PIX_FMT_BGR444LE = 64,
/** packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), big-endian, most significant bits to 1 */
AV_PIX_FMT_BGR444BE = 65,
/** 8bit gray, 8bit alpha */
AV_PIX_FMT_YA8 = 66,
// etc
FrameRate表示视频每秒应该播放的帧数(它与实际录制的图像的数量或时间无关，尽管它为编码比特率提供了基础)。所以，在30 FPS的情况下，为了覆盖20秒的视频，你需要调用record() 30 * 20 = 600次。如果您没有调用record() 600次，那么这就是问题的原因。
VideoBitrate提供视频流应该编码的视频比特率(单位为每秒比特数)。维基百科上有一篇很好的文章。