How to encode grayscale video streams with FFmpeg?

Question

I've got a grayscale video stream coming off a Firewire astronomy camera, I'd like to use FFmpeg to compress the video stream but it will not accept single byte pixel formats for the MPEG1VIDEO codecs. How can I use the FFmpeg API to convert grayscale video frames into a frame format accepted by FFmpeg?

Answer 1

The Relationship of Gray scale and YUV is very simple - The "Y" of YUV is exactly same as Grayscale.

The simpler way to convert the Grayscale in to YUV is

See this reference for Conversion between the scales :

Accordingly :

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)

You can actually use Y[i] = W[i] that will be almost same. The 128 value represents '0' in a scaled/shifted base of 0-256 signed to unsigned conversion.

So all you need to keep is create this other memory area Y and U as the fixed value and provide this frames to ffmpeg.

I am not sure, but by appropriately telling FFMPEG, it does this inside only. The RGB values you supply are equally covered there as well; which is also not native to MPEG.

So look for FFMPEG's API which is able to let you do this.

BONUS
Remember, that in good old days there were Black and white (Gray scale) TV sets. The new color TV sets, needed to be compliant to the old ones, so color information is added in the form of U and V (sometimes it is also called YCbCr - where Cb and Cr are called chroma and are respectively linear variations of UV in this context).

Answer 2

Edit

MPEG-1 only accepts YUV. So convert your frame to yuv. Use the SwsContext structure, create it by calling sws_getContext, and then use sws_scale.

---

Try the rawvideo codec. You will need to specify the pix_fmt parameter which describes the format of your frames - yours are 1-byte per pixel frames, but are they grayscale (you didn't mention)? For example

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

Here pix_fmt specifies yuv420p which is not what you need. Use the appropriate frame type for you.

I'll post the contents of the header file for the pix_fmt values. Try to see if your frame type is defined in it. Look at PIX_FMT_RGB8 (which is 8-bits) for example.

/*
 * copyright (c) 2006 Michael Niedermayer <[e-mail]>
 *
 * 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 3

It works if you simply use "hue" filter; like this:

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