[FFmpeg-devel] [PATCH 1/2] avcodec: add mvdv video decoder

[James Almer]

On 11/25/2019 6:09 PM, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
>  libavcodec/Makefile     |   1 +
>  libavcodec/allcodecs.c  |   1 +
>  libavcodec/avcodec.h    |   1 +
>  libavcodec/codec_desc.c |   7 ++
>  libavcodec/midivid.c    | 272 ++++++++++++++++++++++++++++++++++++++++
>  libavformat/riff.c      |   1 +
>  6 files changed, 283 insertions(+)
>  create mode 100644 libavcodec/midivid.c

[...]

> diff --git a/libavcodec/midivid.c b/libavcodec/midivid.c
> new file mode 100644
> index 0000000000..36ed4b83bd
> --- /dev/null
> +++ b/libavcodec/midivid.c
> @@ -0,0 +1,272 @@
> +/*
> + * MidiVid decoder
> + * Copyright (c) 2019 Paul B Mahol
> + *
> + * 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 <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +
> +#include "libavutil/imgutils.h"
> +#include "libavutil/internal.h"
> +#include "libavutil/intreadwrite.h"
> +#include "libavutil/mem.h"
> +
> +#define BITSTREAM_READER_LE
> +#include "avcodec.h"
> +#include "get_bits.h"
> +#include "bytestream.h"
> +#include "internal.h"
> +
> +typedef struct MidiVidContext {
> +    GetByteContext gb;
> +
> +    uint8_t *uncompressed;
> +    int uncompressed_size;

Should be unsigned int, seeing it's used as argument for
av_fast_padded_malloc().

> +    uint8_t *skip;
> +
> +    AVFrame *frame;
> +} MidiVidContext;
> +
> +static int decode_mvdv(MidiVidContext *s, AVCodecContext *avctx, AVFrame *frame)
> +{
> +    GetByteContext *gb = &s->gb;
> +    GetBitContext mask;
> +    GetByteContext idx9;
> +    uint16_t nb_vectors, intra_flag;
> +    const uint8_t *vec;
> +    const uint8_t *mask_start;
> +    uint8_t *skip;
> +    int mask_size;
> +    int idx9bits = 0;
> +    int idx9val = 0;
> +    int num_blocks;
> +
> +    nb_vectors = bytestream2_get_le16(gb);
> +    intra_flag = bytestream2_get_le16(gb);
> +    if (intra_flag) {
> +        num_blocks = (avctx->width / 2) * (avctx->height / 2);
> +    } else {
> +        int skip_linesize;
> +
> +        num_blocks = bytestream2_get_le32(gb);
> +        skip_linesize = avctx->width >> 1;
> +        mask_start = gb->buffer_start + bytestream2_tell(gb);
> +        mask_size = (avctx->width >> 5) * (avctx->height >> 2);
> +        init_get_bits8(&mask, mask_start, mask_size);
> +        bytestream2_skip(gb, mask_size);
> +        skip = s->skip;
> +
> +        for (int y = 0; y < avctx->height >> 2; y++) {
> +            for (int x = 0; x < avctx->width >> 2; x++) {
> +                int flag = !get_bits1(&mask);
> +
> +                skip[(y*2)  *skip_linesize + x*2  ] = flag;
> +                skip[(y*2)  *skip_linesize + x*2+1] = flag;
> +                skip[(y*2+1)*skip_linesize + x*2  ] = flag;
> +                skip[(y*2+1)*skip_linesize + x*2+1] = flag;
> +            }
> +        }
> +    }
> +
> +    vec = gb->buffer_start + bytestream2_tell(gb);

Isn't this the same as doing vec = g->buffer?

> +    if (bytestream2_get_bytes_left(gb) < nb_vectors * 12)
> +        return AVERROR_INVALIDDATA;
> +    bytestream2_skip(gb, nb_vectors * 12);
> +    if (nb_vectors > 256) {
> +        if (bytestream2_get_bytes_left(gb) < (num_blocks + 7) / 8)
> +            return AVERROR_INVALIDDATA;
> +        bytestream2_init(&idx9, gb->buffer_start + bytestream2_tell(gb), (num_blocks + 7) / 8);

Ditto.