Comment encoder les flux vidéo en niveaux de gris avec FFmpeg?

Question

J'ai un flux vidéo en niveaux de gris sort d'une caméra d'astronomie Firewire, je voudrais utiliser FFmpeg pour compresser le flux vidéo mais il n'accepte pas les formats de pixels d'un seul octet pour les codecs mpeg1video. Comment puis-je utiliser l'API FFmpeg pour convertir des images vidéo en niveaux de gris en un format de trame accepté par FFmpeg?

Answer 1

Modifier

MPEG-1 accepte uniquement YUV. Donc convertir votre image en YUV. Utilisez la structure SwsContext, créez en appelant sws_getContext, puis utilisez sws_scale.

---

Essayez le codec rawvideo. Vous devez spécifier le paramètre pix_fmt qui décrit le format de vos cadres - le vôtre sont 1-octet par des cadres de pixels, mais sont-ils en niveaux de gris (vous ne l'avez pas mentionné)? Par exemple

ffmpeg -i INPUT -vcodec rawvideo -pix_fmt yuv420p output.avi

Ici pix_fmt précise yuv420p qui est pas ce que vous avez besoin. Utilisez le type de cadre approprié pour vous.

Je vais afficher le contenu du fichier d'en-tête pour les valeurs pix_fmt. Essayez de voir si votre type de trame est défini en elle. Look at PIX_FMT_RGB8 (qui est de 8 bits) par exemple.

/*
 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef AVUTIL_PIXFMT_H
#define AVUTIL_PIXFMT_H

/**
 * @file
 * pixel format definitions
 *
 * @warning This file has to be considered an internal but installed
 * header, so it should not be directly included in your projects.
 */

#include "libavutil/avconfig.h"

/**
 * Pixel format. Notes:
 *
 * PIX_FMT_RGB32 is handled in an endian-specific manner. An RGBA
 * color is put together as:
 *  (A << 24) | (R << 16) | (G << 8) | B
 * This is stored as BGRA on little-endian CPU architectures and ARGB on
 * big-endian CPUs.
 *
 * When the pixel format is palettized RGB (PIX_FMT_PAL8), the palettized
 * image data is stored in AVFrame.data[0]. The palette is transported in
 * AVFrame.data[1], is 1024 bytes long (256 4-byte entries) and is
 * formatted the same as in PIX_FMT_RGB32 described above (i.e., it is
 * also endian-specific). Note also that the individual RGB palette
 * components stored in AVFrame.data[1] should be in the range 0..255.
 * This is important as many custom PAL8 video codecs that were designed
 * to run on the IBM VGA graphics adapter use 6-bit palette components.
 *
 * For all the 8bit per pixel formats, an RGB32 palette is in data[1] like
 * for pal8. This palette is filled in automatically by the function
 * allocating the picture.
 *
 * Note, make sure that all newly added big endian formats have pix_fmt&1==1
 *       and that all newly added little endian formats have pix_fmt&1==0
 *       this allows simpler detection of big vs little endian.
 */
enum PixelFormat {
    PIX_FMT_NONE= -1,
    PIX_FMT_YUV420P,   ///< planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)
    PIX_FMT_YUYV422,   ///< packed YUV 4:2:2, 16bpp, Y0 Cb Y1 Cr
    PIX_FMT_RGB24,     ///< packed RGB 8:8:8, 24bpp, RGBRGB...
    PIX_FMT_BGR24,     ///< packed RGB 8:8:8, 24bpp, BGRBGR...
    PIX_FMT_YUV422P,   ///< planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)
    PIX_FMT_YUV444P,   ///< planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples)
    PIX_FMT_YUV410P,   ///< planar YUV 4:1:0,  9bpp, (1 Cr & Cb sample per 4x4 Y samples)
    PIX_FMT_YUV411P,   ///< planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples)
    PIX_FMT_GRAY8,     ///<        Y        ,  8bpp
    PIX_FMT_MONOWHITE, ///<        Y        ,  1bpp, 0 is white, 1 is black, in each byte pixels are ordered from the msb to the lsb
    PIX_FMT_MONOBLACK, ///<        Y        ,  1bpp, 0 is black, 1 is white, in each byte pixels are ordered from the msb to the lsb
    PIX_FMT_PAL8,      ///< 8 bit with PIX_FMT_RGB32 palette
    PIX_FMT_YUVJ420P,  ///< planar YUV 4:2:0, 12bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV420P and setting color_range
    PIX_FMT_YUVJ422P,  ///< planar YUV 4:2:2, 16bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV422P and setting color_range
    PIX_FMT_YUVJ444P,  ///< planar YUV 4:4:4, 24bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV444P and setting color_range
    PIX_FMT_XVMC_MPEG2_MC,///< XVideo Motion Acceleration via common packet passing
    PIX_FMT_XVMC_MPEG2_IDCT,
    PIX_FMT_UYVY422,   ///< packed YUV 4:2:2, 16bpp, Cb Y0 Cr Y1
    PIX_FMT_UYYVYY411, ///< packed YUV 4:1:1, 12bpp, Cb Y0 Y1 Cr Y2 Y3
    PIX_FMT_BGR8,      ///< packed RGB 3:3:2,  8bpp, (msb)2B 3G 3R(lsb)
    PIX_FMT_BGR4,      ///< 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
    PIX_FMT_BGR4_BYTE, ///< packed RGB 1:2:1,  8bpp, (msb)1B 2G 1R(lsb)
    PIX_FMT_RGB8,      ///< packed RGB 3:3:2,  8bpp, (msb)2R 3G 3B(lsb)
    PIX_FMT_RGB4,      ///< 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
    PIX_FMT_RGB4_BYTE, ///< packed RGB 1:2:1,  8bpp, (msb)1R 2G 1B(lsb)
    PIX_FMT_NV12,      ///< 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)
    PIX_FMT_NV21,      ///< as above, but U and V bytes are swapped

    PIX_FMT_ARGB,      ///< packed ARGB 8:8:8:8, 32bpp, ARGBARGB...
    PIX_FMT_RGBA,      ///< packed RGBA 8:8:8:8, 32bpp, RGBARGBA...
    PIX_FMT_ABGR,      ///< packed ABGR 8:8:8:8, 32bpp, ABGRABGR...
    PIX_FMT_BGRA,      ///< packed BGRA 8:8:8:8, 32bpp, BGRABGRA...

    PIX_FMT_GRAY16BE,  ///<        Y        , 16bpp, big-endian
    PIX_FMT_GRAY16LE,  ///<        Y        , 16bpp, little-endian
    PIX_FMT_YUV440P,   ///< planar YUV 4:4:0 (1 Cr & Cb sample per 1x2 Y samples)
    PIX_FMT_YUVJ440P,  ///< planar YUV 4:4:0 full scale (JPEG), deprecated in favor of PIX_FMT_YUV440P and setting color_range
    PIX_FMT_YUVA420P,  ///< planar YUV 4:2:0, 20bpp, (1 Cr & Cb sample per 2x2 Y & A samples)
    PIX_FMT_VDPAU_H264,///< 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
    PIX_FMT_VDPAU_MPEG1,///< 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
    PIX_FMT_VDPAU_MPEG2,///< 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
    PIX_FMT_VDPAU_WMV3,///< 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
    PIX_FMT_VDPAU_VC1, ///< 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
    PIX_FMT_RGB48BE,   ///< packed RGB 16:16:16, 48bpp, 16R, 16G, 16B, the 2-byte value for each R/G/B component is stored as big-endian
    PIX_FMT_RGB48LE,   ///< packed RGB 16:16:16, 48bpp, 16R, 16G, 16B, the 2-byte value for each R/G/B component is stored as little-endian

    PIX_FMT_RGB565BE,  ///< packed RGB 5:6:5, 16bpp, (msb)   5R 6G 5B(lsb), big-endian
    PIX_FMT_RGB565LE,  ///< packed RGB 5:6:5, 16bpp, (msb)   5R 6G 5B(lsb), little-endian
    PIX_FMT_RGB555BE,  ///< packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), big-endian, most significant bit to 0
    PIX_FMT_RGB555LE,  ///< packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), little-endian, most significant bit to 0

    PIX_FMT_BGR565BE,  ///< packed BGR 5:6:5, 16bpp, (msb)   5B 6G 5R(lsb), big-endian
    PIX_FMT_BGR565LE,  ///< packed BGR 5:6:5, 16bpp, (msb)   5B 6G 5R(lsb), little-endian
    PIX_FMT_BGR555BE,  ///< packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), big-endian, most significant bit to 1
    PIX_FMT_BGR555LE,  ///< packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), little-endian, most significant bit to 1

    PIX_FMT_VAAPI_MOCO, ///< 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
    PIX_FMT_VAAPI_IDCT, ///< HW acceleration through VA API at IDCT entry-point, Picture.data[3] contains a vaapi_render_state struct which contains fields extracted from headers
    PIX_FMT_VAAPI_VLD,  ///< 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

    PIX_FMT_YUV420P16LE,  ///< planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
    PIX_FMT_YUV420P16BE,  ///< planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian
    PIX_FMT_YUV422P16LE,  ///< planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
    PIX_FMT_YUV422P16BE,  ///< planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian
    PIX_FMT_YUV444P16LE,  ///< planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
    PIX_FMT_YUV444P16BE,  ///< planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian
    PIX_FMT_VDPAU_MPEG4,  ///< 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
    PIX_FMT_DXVA2_VLD,    ///< HW decoding through DXVA2, Picture.data[3] contains a LPDIRECT3DSURFACE9 pointer

    PIX_FMT_RGB444LE,  ///< packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), little-endian, most significant bits to 0
    PIX_FMT_RGB444BE,  ///< packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), big-endian, most significant bits to 0
    PIX_FMT_BGR444LE,  ///< packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), little-endian, most significant bits to 1
    PIX_FMT_BGR444BE,  ///< packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), big-endian, most significant bits to 1
    PIX_FMT_GRAY8A,    ///< 8bit gray, 8bit alpha
    PIX_FMT_BGR48BE,   ///< packed RGB 16:16:16, 48bpp, 16B, 16G, 16R, the 2-byte value for each R/G/B component is stored as big-endian
    PIX_FMT_BGR48LE,   ///< packed RGB 16:16:16, 48bpp, 16B, 16G, 16R, the 2-byte value for each R/G/B component is stored as little-endian

    //the following 10 formats have the disadvantage of needing 1 format for each bit depth, thus
    //If you want to support multiple bit depths, then using PIX_FMT_YUV420P16* with the bpp stored seperately
    //is better
    PIX_FMT_YUV420P9BE, ///< planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian
    PIX_FMT_YUV420P9LE, ///< planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
    PIX_FMT_YUV420P10BE,///< planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian
    PIX_FMT_YUV420P10LE,///< planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
    PIX_FMT_YUV422P10BE,///< planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
    PIX_FMT_YUV422P10LE,///< planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian
    PIX_FMT_YUV444P9BE, ///< planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
    PIX_FMT_YUV444P9LE, ///< planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian
    PIX_FMT_YUV444P10BE,///< planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
    PIX_FMT_YUV444P10LE,///< planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian

    PIX_FMT_NB,        ///< number of pixel formats, DO NOT USE THIS if you want to link with shared libav* because the number of formats might differ between versions
};

#define PIX_FMT_Y400A PIX_FMT_GRAY8A

#if AV_HAVE_BIGENDIAN
#   define PIX_FMT_NE(be, le) PIX_FMT_##be
#else
#   define PIX_FMT_NE(be, le) PIX_FMT_##le
#endif

#define PIX_FMT_RGB32   PIX_FMT_NE(ARGB, BGRA)
#define PIX_FMT_RGB32_1 PIX_FMT_NE(RGBA, ABGR)
#define PIX_FMT_BGR32   PIX_FMT_NE(ABGR, RGBA)
#define PIX_FMT_BGR32_1 PIX_FMT_NE(BGRA, ARGB)

#define PIX_FMT_GRAY16 PIX_FMT_NE(GRAY16BE, GRAY16LE)
#define PIX_FMT_RGB48  PIX_FMT_NE(RGB48BE,  RGB48LE)
#define PIX_FMT_RGB565 PIX_FMT_NE(RGB565BE, RGB565LE)
#define PIX_FMT_RGB555 PIX_FMT_NE(RGB555BE, RGB555LE)
#define PIX_FMT_RGB444 PIX_FMT_NE(RGB444BE, RGB444LE)
#define PIX_FMT_BGR48  PIX_FMT_NE(BGR48BE,  BGR48LE)
#define PIX_FMT_BGR565 PIX_FMT_NE(BGR565BE, BGR565LE)
#define PIX_FMT_BGR555 PIX_FMT_NE(BGR555BE, BGR555LE)
#define PIX_FMT_BGR444 PIX_FMT_NE(BGR444BE, BGR444LE)

#define PIX_FMT_YUV420P9  PIX_FMT_NE(YUV420P9BE , YUV420P9LE)
#define PIX_FMT_YUV444P9  PIX_FMT_NE(YUV444P9BE , YUV444P9LE)
#define PIX_FMT_YUV420P10 PIX_FMT_NE(YUV420P10BE, YUV420P10LE)
#define PIX_FMT_YUV422P10 PIX_FMT_NE(YUV422P10BE, YUV422P10LE)
#define PIX_FMT_YUV444P10 PIX_FMT_NE(YUV444P10BE, YUV444P10LE)
#define PIX_FMT_YUV420P16 PIX_FMT_NE(YUV420P16BE, YUV420P16LE)
#define PIX_FMT_YUV422P16 PIX_FMT_NE(YUV422P16BE, YUV422P16LE)
#define PIX_FMT_YUV444P16 PIX_FMT_NE(YUV444P16BE, YUV444P16LE)

#endif /* AVUTIL_PIXFMT_H */ 

Answer 2

La relation d'échelle de gris et YUV est très simple - Le « Y » est exactement de même YUV que Niveaux de gris.

La façon plus simple de convertir les nuances de gris en YUV est

Voir cette référence pour la conversion entre les échelles:

En conséquence:

Y  =      (0.257 * R) + (0.504 * G) + (0.098 * B) + 16
Cr = V =  (0.439 * R) - (0.368 * G) - (0.071 * B) + 128
Cb = U = -(0.148 * R) - (0.291 * G) + (0.439 * B) + 128

Now: 
For a Grayscale image (W): 

R = W;
G = W;
B = W;

Keeping this: 

Y[i] = 0.895 * W[i] + 16. 
U[i] = 128 (fixed value)
V[i] = 128 (fxied value)

Vous pouvez réellement utiliser Y [i] = W [i] qui sera presque la même. La valeur 128 représente « 0 » dans une base mise à l'échelle / décalée de 0-256 signé à la conversion sans signe.

Donc tout ce que vous devez garder est de créer cette autre zone de mémoire Y et U en tant que valeur fixe et de fournir ces images à ffmpeg.

Je ne suis pas sûr, mais en disant de façon appropriée FFMPEG, il le fait à l'intérieur seulement. Les valeurs RVB que vous fournissez sont également couverts là aussi; qui est aussi pas natif MPEG.

regard pour l'API de FFMPEG qui est en mesure de vous laisser faire cela.

BONUS Rappelez-vous que, dans bon vieux temps, il y avait des téléviseurs noir et blanc (échelle de gris). Les nouveaux téléviseurs couleur, nécessaires pour être conformes aux anciens, afin que les informations de couleur est ajoutée sous forme de U et V (parfois il est aussi appelé YCbCr - où Cb et Cr sont appelés chroma et des variations respectivement linéaires des UV ce contexte).

Answer 3

Il fonctionne si vous utilisez simplement le filtre « de couleur »; comme ceci:

ffmpeg -i inputfile.ogv -vf teinte = s = 0 outputfile-unsat.ogv