[FFmpeg-devel] [PATCH] libavcodec/pgx: Added pgx decoder

Gautam Ramakrishnan gautamramk at gmail.com
Thu Jun 25 09:49:34 EEST 2020


On Thu, Jun 25, 2020 at 12:43 AM Nicolas George <george at nsup.org> wrote:
>
> Thanks for the patch. Here are a few preliminary remarks.
>
> gautamramk at gmail.com (12020-06-24):
> > From: Gautam Ramakrishnan <gautamramk at gmail.com>
> >
> > This patch support to read and decode
> > pgx files.
> > ---
> >  libavcodec/Makefile      |   1 +
> >  libavcodec/allcodecs.c   |   1 +
> >  libavcodec/codec_id.h    |   1 +
> >  libavcodec/pgx.h         |  38 +++++++++
> >  libavcodec/pgxdec.c      | 176 +++++++++++++++++++++++++++++++++++++++
> >  libavformat/allformats.c |   1 +
> >  libavformat/img2dec.c    |  11 +++
> >  7 files changed, 229 insertions(+)
> >  create mode 100644 libavcodec/pgx.h
> >  create mode 100644 libavcodec/pgxdec.c
>
> Documentation?
>
> >
> > diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> > index 5a6ea59715..0198c244e0 100644
> > --- a/libavcodec/Makefile
> > +++ b/libavcodec/Makefile
> > @@ -533,6 +533,7 @@ OBJS-$(CONFIG_PCX_ENCODER)             += pcxenc.o
> >  OBJS-$(CONFIG_PFM_DECODER)             += pnmdec.o pnm.o
> >  OBJS-$(CONFIG_PGM_DECODER)             += pnmdec.o pnm.o
> >  OBJS-$(CONFIG_PGM_ENCODER)             += pnmenc.o
> > +OBJS-$(CONFIG_PGX_DECODER)             += pgxdec.o
> >  OBJS-$(CONFIG_PGMYUV_DECODER)          += pnmdec.o pnm.o
> >  OBJS-$(CONFIG_PGMYUV_ENCODER)          += pnmenc.o
> >  OBJS-$(CONFIG_PGSSUB_DECODER)          += pgssubdec.o
> > diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> > index fa0c08d42e..b0217e6d6a 100644
> > --- a/libavcodec/allcodecs.c
> > +++ b/libavcodec/allcodecs.c
> > @@ -236,6 +236,7 @@ extern AVCodec ff_pcx_decoder;
> >  extern AVCodec ff_pfm_decoder;
> >  extern AVCodec ff_pgm_encoder;
> >  extern AVCodec ff_pgm_decoder;
> > +extern AVCodec ff_pgx_decoder;
> >  extern AVCodec ff_pgmyuv_encoder;
> >  extern AVCodec ff_pgmyuv_decoder;
> >  extern AVCodec ff_pictor_decoder;
> > diff --git a/libavcodec/codec_id.h b/libavcodec/codec_id.h
> > index d885962c9c..027ef21c62 100644
> > --- a/libavcodec/codec_id.h
> > +++ b/libavcodec/codec_id.h
> > @@ -111,6 +111,7 @@ enum AVCodecID {
> >      AV_CODEC_ID_PPM,
> >      AV_CODEC_ID_PBM,
> >      AV_CODEC_ID_PGM,
> > +    AV_CODEC_ID_PGX,
> >      AV_CODEC_ID_PGMYUV,
> >      AV_CODEC_ID_PAM,
> >      AV_CODEC_ID_FFVHUFF,
> > diff --git a/libavcodec/pgx.h b/libavcodec/pgx.h
> > new file mode 100644
> > index 0000000000..bbe93fafe7
> > --- /dev/null
> > +++ b/libavcodec/pgx.h
> > @@ -0,0 +1,38 @@
> > +/*
> > + * PGX image format
> > + * Copyright (c) 2020 Gautam Ramakrishnan
> > + *
> > + * 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 AVCODEC_PGX_H
> > +#define AVCODEC_PGX_H
> > +
> > +#include "avcodec.h"
> > +#include "bytestream.h"
> > +
>
> > +typedef struct PGXContext {
> > +    GetByteContext  g;
> > +    int depth;
>
> > +    int sgnd;
>
> Is the micro-economy of letters rly ncssry?
>
> > +    int width;
> > +    int height;
> > +} PGXContext;
> > +
> > +int ff_pgx_decode_header(AVCodecContext *avctx, PGXContext * const s);
>
> This is not compatible with the function definition, how did you not get
> a warning from the compiler?
>
> Nit: no space after pointer mark.
>
> Will this be used elsewhere? Probably not. Then put it directly in the
> source file.
>
> > +
> > +#endif /* AVCODEC_PNM_H */
>
> > \ No newline at end of file
>
> You need to fix the config of your text editor.
>
> > diff --git a/libavcodec/pgxdec.c b/libavcodec/pgxdec.c
> > new file mode 100644
> > index 0000000000..233bf34717
> > --- /dev/null
> > +++ b/libavcodec/pgxdec.c
> > @@ -0,0 +1,176 @@
> > +/*
> > + * PGX image format
> > + * Copyright (c) 2020 Gautam Ramakrishnan
> > + *
> > + * 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
> > + */
> > +
> > +#include "avcodec.h"
> > +#include "internal.h"
> > +#include "pgx.h"
> > +
> > +static int pgx_get_number(AVCodecContext *avctx, PGXContext * const s) {
> > +    char number[10];
> > +    int i;
> > +    int ret;
> > +    number[9] = '\0';
> > +    for (i = 0; i < 9; i++) {
> > +        if (!bytestream2_get_bytes_left(&s->g))
> > +            return AVERROR_INVALIDDATA;
>
> > +        number[i] = (char)bytestream2_get_byteu(&s->g);
>
> The cast is useless and harmful. Same in other places.
The type conversions confused me a bit. I will remove them.
I guess changing from bytestream2_get_byteu to bytestrea2_get_byte should
do the trick here?
>
> > +        if (number[i] == ' ' || number[i] == 0xA || number[i] == 0xD) {
> > +            number[i] = '\0';
> > +            break;
> > +        } else if (number[i] < '0' || number[i] > '9') {
> > +            return AVERROR_INVALIDDATA;
> > +        }
> > +    }
> > +    if (i > 9)
> > +        return AVERROR_INVALIDDATA;
>
> > +    ret = (int)strtol(number, NULL, 10);
>
> Looks extra complicated just to use strtol(). Just convert from decimal
> to number in the loop.
>
Yep, I shall change this. Skipped my mind while writing code.
> > +    if (ret >= 0)
> > +        return ret;
> > +    return AVERROR_INVALIDDATA;
> > +}
> > +
> > +int ff_pgx_decode_header(AVCodecContext *avctx, PGXContext * s)
> > +{
> > +    const char *header_start = "PG ML ";
> > +    int i;
> > +    int byte;
> > +    if (bytestream2_get_bytes_left(&s->g) < 13) {
> > +        return AVERROR_INVALIDDATA;
> > +    }
> > +
> > +    for (i = 0; i < 6; i++) {
> > +        if (header_start[i] != (char)bytestream2_get_byteu(&s->g)) {
> > +            return AVERROR_INVALIDDATA;
> > +        }
> > +    }
> > +    byte = bytestream2_peek_byte(&s->g);
> > +    if (byte == '+') {
> > +        s->sgnd = 0;
> > +        bytestream2_skip(&s->g, 1);
> > +    } else if (byte == '-') {
> > +        s->sgnd = 1;
> > +        bytestream2_skip(&s->g, 1);
> > +    }
> > +
> > +    if (bytestream2_peek_byte(&s->g) == ' ')
> > +        bytestream2_skip(&s->g, 1);
> > +    s->depth = pgx_get_number(avctx, s);
> > +    s->width = pgx_get_number(avctx, s);
> > +    s->height = pgx_get_number(avctx, s);
> > +    if (bytestream2_peek_byte(&s->g) == 0xA)
> > +        bytestream2_skip(&s->g, 1);
> > +    return 0;
> > +}
> > +
> > +static inline int write_frame_16(AVPacket *avpkt, AVFrame *frame, PGXContext * const s)
> > +{
> > +    int i, j;
> > +    for (i = 0; i < s->height; i++) {
>
> > +        uint16_t* line = (uint16_t*)frame->data[0] + i*frame->linesize[0]/2;
>
> Pointer mark belongs with the variable, not with the type.
>
> > +        for (j = 0; j < s->width; j++) {
> > +            int val;
> > +            if (s->sgnd) {
> > +                val = (int16_t)bytestream2_get_be16(&s->g) + (1 << (s->depth - 1));
> > +                val <<= (16 - s->depth);
> > +                *(line + j) = val;
> > +            } else {
> > +                val = bytestream2_get_be16u(&s->g);
> > +                val <<= (16 - s->depth);
> > +                *(line + j) = val;
> > +            }
> > +        }
> > +        line += frame->linesize[0]/2;
> > +    }
> > +    return 0;
> > +}
> > +
> > +static inline int write_frame_8(AVPacket *avpkt, AVFrame *frame, PGXContext * const s)
> > +{
> > +    int i, j;
> > +    for (i = 0; i < s->height; i++) {
> > +        uint8_t* line = frame->data[0] + i*frame->linesize[0];
> > +        for (j = 0; j < s->width; j++) {
> > +            int val;
> > +            if (s->sgnd) {
> > +                val = bytestream2_get_byte(&s->g) + (1 << (s->depth - 1));
> > +                val <<= (8 - s->depth);
> > +                *(line + j) = val;
> > +            } else {
> > +                val = bytestream2_get_byteu(&s->g);
> > +                val <<= (8 - s->depth);
> > +                *(line + j) = val;
> > +            }
> > +        }
> > +        line += frame->linesize[0];
> > +    }
> > +    return 0;
> > +}
> > +
> > +static int pgx_decode_frame(AVCodecContext *avctx, void *data,
> > +                            int *got_frame, AVPacket *avpkt)
> > +{
> > +    PGXContext * s = avctx->priv_data;
> > +    AVFrame * const p    = data;
> > +    int ret;
> > +    int num_vals;
> > +    int bpp;
> > +    bytestream2_init(&s->g, avpkt->data, avpkt->size);
>
> > +    if ((ret = ff_pgx_decode_header(avctx, s)) < 0)
> > +        return ret;
>
> Since you decode the header each time (normal for an image format), most
> of the fields do not need to be in the persistent context.
>
So you mean to say no need to store height and width in the
PGX context?
> > +
> > +    num_vals = s->width * s->height;
> > +
> > +    if (ret = ff_set_dimensions(avctx, s->width, s->height) < 0)
> > +        return ret;
> > +
> > +    if (s->depth <= 8) {
> > +        avctx->pix_fmt = AV_PIX_FMT_GRAY8;
> > +        bpp = 8;
> > +    } else if (s->depth <= 16) {
> > +        avctx->pix_fmt = AV_PIX_FMT_GRAY16BE;
> > +        bpp = 16;
> > +    } else {
> > +        av_log(avctx, AV_LOG_ERROR, "Maximum depth of 16 bits supported.\n");
> > +        return AVERROR_PATCHWELCOME;
> > +    }
> > +
> > +    if ((ret = ff_get_buffer(avctx, p, 0)) < 0)
> > +        return ret;
> > +    *got_frame = 1;
> > +    p->pict_type = AV_PICTURE_TYPE_I;
> > +    p->key_frame = 1;
> > +    avctx->bits_per_raw_sample = s->depth;
> > +    if (bpp == 8)
> > +        write_frame_8(avpkt, p, s);
> > +    else if (bpp == 16)
> > +        write_frame_16(avpkt, p, s);
> > +    return 0;
> > +}
> > +
> > +AVCodec ff_pgx_decoder = {
> > +    .name           = "pgx",
> > +    .long_name      = NULL_IF_CONFIG_SMALL("PGX image"),
> > +    .type           = AVMEDIA_TYPE_VIDEO,
> > +    .id             = AV_CODEC_ID_PGX,
> > +    .priv_data_size = sizeof(PGXContext),
> > +    .decode         = pgx_decode_frame,
> > +    .capabilities   = AV_CODEC_CAP_DR1,
> > +};
> > \ No newline at end of file
> > diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> > index 97fd06debb..f8527b1fd4 100644
> > --- a/libavformat/allformats.c
> > +++ b/libavformat/allformats.c
> > @@ -488,6 +488,7 @@ extern AVInputFormat  ff_image_pbm_pipe_demuxer;
> >  extern AVInputFormat  ff_image_pcx_pipe_demuxer;
> >  extern AVInputFormat  ff_image_pgmyuv_pipe_demuxer;
> >  extern AVInputFormat  ff_image_pgm_pipe_demuxer;
> > +extern AVInputFormat  ff_image_pgx_pipe_demuxer;
> >  extern AVInputFormat  ff_image_pictor_pipe_demuxer;
> >  extern AVInputFormat  ff_image_png_pipe_demuxer;
> >  extern AVInputFormat  ff_image_ppm_pipe_demuxer;
> > diff --git a/libavformat/img2dec.c b/libavformat/img2dec.c
> > index ee7ceed08f..43270901ff 100644
> > --- a/libavformat/img2dec.c
> > +++ b/libavformat/img2dec.c
> > @@ -1000,6 +1000,16 @@ static int pgmyuv_probe(const AVProbeData *p) // custom FFmpeg format recognized
> >      return ret && av_match_ext(p->filename, "pgmyuv") ? ret : 0;
> >  }
> >
> > +static int pgx_probe(const AVProbeData *p)
> > +{
> > +    const uint8_t *b = p->buf;
> > +    int ret = (AV_RB32(b) & 0xFFFFFF00) == 0x50472000;
> > +    ret = ret && av_match_ext(p->filename, "pgx");
> > +    if (ret)
> > +        return AVPROBE_SCORE_EXTENSION + 1;
> > +    return 0;
> > +}
> > +
> >  static int ppm_probe(const AVProbeData *p)
> >  {
> >      return pnm_magic_check(p, 3) || pnm_magic_check(p, 6) ? pnm_probe(p) : 0;
> > @@ -1094,6 +1104,7 @@ IMAGEAUTO_DEMUXER(pbm,     AV_CODEC_ID_PBM)
> >  IMAGEAUTO_DEMUXER(pcx,     AV_CODEC_ID_PCX)
> >  IMAGEAUTO_DEMUXER(pgm,     AV_CODEC_ID_PGM)
> >  IMAGEAUTO_DEMUXER(pgmyuv,  AV_CODEC_ID_PGMYUV)
> > +IMAGEAUTO_DEMUXER(pgx,     AV_CODEC_ID_PGX)
> >  IMAGEAUTO_DEMUXER(pictor,  AV_CODEC_ID_PICTOR)
> >  IMAGEAUTO_DEMUXER(png,     AV_CODEC_ID_PNG)
> >  IMAGEAUTO_DEMUXER(ppm,     AV_CODEC_ID_PPM)
>
> Regards,
>
> --
>   Nicolas George

Thanks for the review Nicolas, I shall make the changes

-- 
-------------
Gautam |


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