[FFmpeg-devel] [PATCH 1/2] avfilter: add readvitc filter

Paul B Mahol onemda at gmail.com
Fri Apr 8 11:23:52 CEST 2016


On 4/8/16, Tobias Rapp <t.rapp at noa-archive.com> wrote:
> Add a filter to scan the top lines of video frames for vertical interval
> timecode (VITC) information and attach it as metadata keys.
>
> Signed-off-by: Tobias Rapp <t.rapp at noa-archive.com>
> ---
>  Changelog                 |   1 +
>  MAINTAINERS               |   1 +
>  doc/filters.texi          |  26 +++++
>  libavfilter/Makefile      |   1 +
>  libavfilter/allfilters.c  |   1 +
>  libavfilter/version.h     |   4 +-
>  libavfilter/vf_readvitc.c | 249
> ++++++++++++++++++++++++++++++++++++++++++++++
>  7 files changed, 281 insertions(+), 2 deletions(-)
>  create mode 100644 libavfilter/vf_readvitc.c
>
> diff --git a/Changelog b/Changelog
> index b4a4dd7..51613d6 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -22,6 +22,7 @@ version <next>:
>  - musx demuxer
>  - aix demuxer
>  - remap filter
> +- readvitc filter
>
>  version 3.0:
>  - Common Encryption (CENC) MP4 encoding and decoding support
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a993a67..d2593e5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -385,6 +385,7 @@ Filters:
>    vf_neighbor.c                         Paul B Mahol
>    vf_psnr.c                             Paul B Mahol
>    vf_random.c                           Paul B Mahol
> +  vf_readvitc.c                         Tobias Rapp (CC t.rapp at
> noa-archive dot com)
>    vf_scale.c                            Michael Niedermayer
>    vf_separatefields.c                   Paul B Mahol
>    vf_ssim.c                             Paul B Mahol
> diff --git a/doc/filters.texi b/doc/filters.texi
> index e848584..12a902e 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -10430,6 +10430,32 @@ less than @code{0}, the filter will try to use a
> good random seed on a
>  best effort basis.
>  @end table
>
> + at section readvitc
> +
> +Read vertical interval timecode (VITC) information from the top lines of a
> +video frame.
> +
> +The filter adds frame metadata key @code{lavfi.readvitc.tc_str} with the
> +timecode value, if a valid timecode has been detected. Further metadata key
> + at code{lavfi.readvitc.found} is set to 0/1 depending on whether
> +timecode data has been found or not.
> +
> +This filter accepts the following options:
> +
> + at table @option
> + at item scan_max
> +Set the maximum number of lines to scan for VITC data. If the value is set
> to
> + at code{-1} the full video frame is scanned. Default is @code{45}.
> +
> + at item thr_b
> +Set the luma threshold for black. Accepts float numbers in the range
> [0.0,1.0],
> +default value is @code{0.2}. The value must be smaller than @code{thr_w}.
> +
> + at item thr_w
> +Set the luma threshold for white. Accepts float numbers in the range
> [0.0,1.0],
> +default value is @code{0.6}. The value must be larger than @code{thr_b}.
> + at end table
> +
>  @section remap
>
>  Remap pixels using 2nd: Xmap and 3rd: Ymap input video stream.
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 3a3de48..0994d46 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -223,6 +223,7 @@ OBJS-$(CONFIG_PSNR_FILTER)                   +=
> vf_psnr.o dualinput.o framesync.
>  OBJS-$(CONFIG_PULLUP_FILTER)                 += vf_pullup.o
>  OBJS-$(CONFIG_QP_FILTER)                     += vf_qp.o
>  OBJS-$(CONFIG_RANDOM_FILTER)                 += vf_random.o
> +OBJS-$(CONFIG_READVITC_FILTER)               += vf_readvitc.o
>  OBJS-$(CONFIG_REALTIME_FILTER)               += f_realtime.o
>  OBJS-$(CONFIG_REMAP_FILTER)                  += vf_remap.o framesync.o
>  OBJS-$(CONFIG_REMOVEGRAIN_FILTER)            += vf_removegrain.o
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index b6f4a2c..d59b2d8 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -243,6 +243,7 @@ void avfilter_register_all(void)
>      REGISTER_FILTER(PULLUP,         pullup,         vf);
>      REGISTER_FILTER(QP,             qp,             vf);
>      REGISTER_FILTER(RANDOM,         random,         vf);
> +    REGISTER_FILTER(READVITC,       readvitc,       vf);
>      REGISTER_FILTER(REALTIME,       realtime,       vf);
>      REGISTER_FILTER(REMAP,          remap,          vf);
>      REGISTER_FILTER(REMOVEGRAIN,    removegrain,    vf);
> diff --git a/libavfilter/version.h b/libavfilter/version.h
> index 4cb5a2e..48b9d9a 100644
> --- a/libavfilter/version.h
> +++ b/libavfilter/version.h
> @@ -30,8 +30,8 @@
>  #include "libavutil/version.h"
>
>  #define LIBAVFILTER_VERSION_MAJOR   6
> -#define LIBAVFILTER_VERSION_MINOR  41
> -#define LIBAVFILTER_VERSION_MICRO 101
> +#define LIBAVFILTER_VERSION_MINOR  42
> +#define LIBAVFILTER_VERSION_MICRO 100
>
>  #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
>                                                 LIBAVFILTER_VERSION_MINOR, \
> diff --git a/libavfilter/vf_readvitc.c b/libavfilter/vf_readvitc.c
> new file mode 100644
> index 0000000..9bb7220
> --- /dev/null
> +++ b/libavfilter/vf_readvitc.c
> @@ -0,0 +1,249 @@
> +/*
> + * Copyright (c) 2016 Tobias Rapp
> + *
> + * 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
> + */
> +
> +/**
> + * @file
> + * Filter for reading the vertical interval timecode (VITC).
> + * See also https://en.wikipedia.org/wiki/Vertical_interval_timecode
> + */
> +
> +#include "libavutil/common.h"
> +#include "libavutil/internal.h"
> +#include "libavutil/opt.h"
> +#include "libavutil/timecode.h"
> +#include "avfilter.h"
> +#include "formats.h"
> +#include "internal.h"
> +
> +#define LINE_DATA_SIZE 9
> +
> +typedef struct ReadVitcContext {
> +    const AVClass *class;
> +
> +    int scan_max;
> +    double thr_b;
> +    double thr_w;
> +
> +    int threshold_black;
> +    int threshold_white;
> +    int threshold_gray;
> +    int grp_width;
> +    uint8_t line_data[LINE_DATA_SIZE];
> +    char tcbuf[AV_TIMECODE_STR_SIZE];
> +} ReadVitcContext;
> +
> +#define OFFSET(x) offsetof(ReadVitcContext, x)
> +#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
> +
> +static const AVOption readvitc_options[] = {
> +    { "scan_max", "maximum line numbers to scan for VITC data",
> OFFSET(scan_max), AV_OPT_TYPE_INT, {.i64 = 45 }, -1, INT_MAX, FLAGS },
> +    { "thr_b",    "black color threshold", OFFSET(thr_b),
> AV_OPT_TYPE_DOUBLE, {.dbl = 0.2 }, 0, 1.0, FLAGS },
> +    { "thr_w",    "white color threshold", OFFSET(thr_w),
> AV_OPT_TYPE_DOUBLE, {.dbl = 0.6 }, 0, 1.0, FLAGS },
> +    { NULL }
> +};
> +
> +AVFILTER_DEFINE_CLASS(readvitc);
> +
> +static uint8_t get_vitc_crc( uint8_t *line ) {
> +    uint8_t crc;
> +
> +    crc = (0x01 | (line[0] << 2));
> +    crc ^= ((line[0] >> 6) | 0x04 | (line[1] << 4));
> +    crc ^= ((line[1] >> 4) | 0x10 | (line[2] << 6));
> +    crc ^= ((line[2] >> 2) | 0x40);
> +    crc ^= line[3];
> +    crc ^= (0x01 | (line[4] << 2));
> +    crc ^= ((line[4] >> 6) | 0x04 | (line[5] << 4));
> +    crc ^= ((line[5] >> 4) | 0x10 | (line[6] << 6));
> +    crc ^= ((line[6] >> 2) | 0x40);
> +    crc ^= line[7];
> +    crc ^= 0x01;
> +    crc = (crc >> 2) | (crc << 6);  // rotate byte right by two bits
> +    return crc;
> +}
> +
> +static inline uint8_t get_pit_avg3( uint8_t *line, int i ) {
> +    return ((line[i-1] + line[i] + line[i+1]) / 3);
> +}
> +
> +static int read_vitc_line( ReadVitcContext *ctx, uint8_t *src, int
> line_size, int width, int height )
> +{
> +    uint8_t *scan_line;
> +    int grp_index, pit_index;
> +    int grp_start_pos;
> +    uint8_t pit_value;
> +    int x, y, res = 0;
> +
> +    if (ctx->scan_max >= 0)
> +        height = FFMIN(height, ctx->scan_max);
> +
> +    // scan lines for VITC data, starting from the top
> +    for (y = 0; y < height; y++) {
> +        scan_line = src;
> +        memset(ctx->line_data, 0, LINE_DATA_SIZE);
> +        grp_index = 0;
> +        x = 0;
> +        while ((x < width) && (grp_index < 9)) {
> +            // search next sync pattern
> +            while ((x < width) && (scan_line[x] < ctx->threshold_white))
> +                x++;
> +            while ((x < width) && (scan_line[x] > ctx->threshold_black))
> +                x++;
> +            x = FFMAX(x - ((ctx->grp_width+10) / 20), 1);  // step back a
> half pit
> +            grp_start_pos = x;
> +            if ((grp_start_pos + ctx->grp_width) > width)
> +                break;  // not enough pixels for reading a whole pit group
> +            pit_value = get_pit_avg3(scan_line, x);
> +            if (pit_value < ctx->threshold_white)
> +               break;  // first sync bit mismatch
> +            x = grp_start_pos + ((ctx->grp_width) / 10);
> +            pit_value = get_pit_avg3(scan_line, x);
> +            if (pit_value > ctx->threshold_black )
> +                break;  // second sync bit mismatch
> +            for (pit_index = 0; pit_index <= 7; pit_index++) {
> +                x = grp_start_pos + (((pit_index+2)*ctx->grp_width) / 10);
> +                pit_value = get_pit_avg3(scan_line, x);
> +                if (pit_value > ctx->threshold_gray)
> +                    ctx->line_data[grp_index] |= (1 << pit_index);
> +            }
> +            grp_index++;
> +        }
> +        if ((grp_index == 9) && (get_vitc_crc(ctx->line_data) ==
> ctx->line_data[8])) {
> +            res = 1;
> +            break;
> +        }
> +        src += line_size;
> +    }
> +
> +    return res;
> +}
> +
> +static unsigned bcd2uint(uint8_t high, uint8_t low)
> +{
> +   if (high > 9 || low > 9)
> +       return 0;
> +   return 10*high + low;
> +}
> +
> +static char *make_vitc_tc_string(char *buf, uint8_t *line)
> +{
> +    unsigned hh   = bcd2uint(line[7] & 0x03, line[6] & 0x0f);  // 6-bit
> hours
> +    unsigned mm   = bcd2uint(line[5] & 0x07, line[4] & 0x0f);  // 7-bit
> minutes
> +    unsigned ss   = bcd2uint(line[3] & 0x07, line[2] & 0x0f);  // 7-bit
> seconds
> +    unsigned ff   = bcd2uint(line[1] & 0x03, line[0] & 0x0f);  // 6-bit
> frames
> +    unsigned drop = (line[1] & 0x04);                          // 1-bit
> drop flag
> +    snprintf(buf, AV_TIMECODE_STR_SIZE, "%02u:%02u:%02u%c%02u",
> +             hh, mm, ss, drop ? ';' : ':', ff);
> +    return buf;
> +}
> +
> +static av_cold int init(AVFilterContext *ctx)
> +{
> +    ReadVitcContext *s = ctx->priv;
> +
> +    s->threshold_black = s->thr_b * UINT8_MAX;
> +    s->threshold_white = s->thr_w * UINT8_MAX;
> +    if (s->threshold_black >= s->threshold_white) {
> +        av_log(ctx, AV_LOG_WARNING, "Black color threshold '%d' is higher
> than white color threshold '%d'\n",
> +                s->threshold_black, s->threshold_white);
> +        return AVERROR(EINVAL);
> +    }
> +    s->threshold_gray = s->threshold_white - ((s->threshold_white -
> s->threshold_black) / 2);
> +    av_log(ctx, AV_LOG_DEBUG, "threshold_black:%d threshold_white:%d
> threshold_gray:%d\n",
> +            s->threshold_black, s->threshold_white, s->threshold_gray);
> +
> +    return 0;
> +}
> +
> +static int config_props(AVFilterLink *inlink)
> +{
> +    AVFilterContext *ctx = inlink->dst;
> +    ReadVitcContext *s = ctx->priv;
> +
> +    s->grp_width = inlink->w * 5 / 48;
> +    av_log(ctx, AV_LOG_DEBUG, "w:%d h:%d grp_width:%d scan_max:%d\n",
> +            inlink->w, inlink->h, s->grp_width, s->scan_max);
> +    return 0;
> +}
> +
> +static int query_formats(AVFilterContext *ctx)
> +{
> +    static const enum AVPixelFormat pixel_fmts_eq[] = {
> +        AV_PIX_FMT_GRAY8,
> +        AV_PIX_FMT_YUV410P,
> +        AV_PIX_FMT_YUV411P,
> +        AV_PIX_FMT_YUV420P,
> +        AV_PIX_FMT_YUV422P,
> +        AV_PIX_FMT_YUV444P,

AV_PIX_FMT_YUV440P? Also J variants...

> +        AV_PIX_FMT_NONE
> +    };
> +    AVFilterFormats *fmts_list = ff_make_format_list(pixel_fmts_eq);
> +    if (!fmts_list)
> +        return AVERROR(ENOMEM);
> +    return ff_set_common_formats(ctx, fmts_list);
> +}
> +
> +static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
> +{
> +    AVFilterContext *ctx = inlink->dst;
> +    AVFilterLink *outlink = ctx->outputs[0];
> +    ReadVitcContext *s = ctx->priv;
> +    int found;
> +
> +    found = read_vitc_line(s, frame->data[0], frame->linesize[0],
> inlink->w, inlink->h);
> +    av_dict_set(&frame->metadata, "lavfi.readvitc.found", (found ? "1" :
> "0"), 0);
> +    if (found)
> +        av_dict_set(&frame->metadata, "lavfi.readvitc.tc_str",
> make_vitc_tc_string(s->tcbuf, s->line_data), 0);
> +
> +    return ff_filter_frame(outlink, frame);
> +}
> +
> +#if CONFIG_READVITC_FILTER

Not needed.

> +
> +static const AVFilterPad inputs[] = {
> +    {
> +        .name         = "default",
> +        .type         = AVMEDIA_TYPE_VIDEO,
> +        .filter_frame = filter_frame,
> +        .config_props = config_props,
> +    },
> +    { NULL }
> +};
> +
> +static const AVFilterPad outputs[] = {
> +    {
> +        .name = "default",
> +        .type = AVMEDIA_TYPE_VIDEO,
> +    },
> +    { NULL }
> +};
> +
> +AVFilter ff_vf_readvitc = {
> +    .name          = "readvitc",
> +    .description   = NULL_IF_CONFIG_SMALL("Read vertical interval timecode
> and write it to frame metadata."),
> +    .priv_size     = sizeof(ReadVitcContext),
> +    .priv_class    = &readvitc_class,
> +    .inputs        = inputs,
> +    .outputs       = outputs,
> +    .init          = init,
> +    .query_formats = query_formats,
> +};
> +
> +#endif /* CONFIG_READVITC_FILTER */

Not needed.

> --
> 1.9.1
>
>
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