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

[Paul B Mahol]

On 11/26/19, James Almer <jamrial at gmail.com> wrote:
> 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().

Ok.

>
>> +    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?

No point in changing now.

>
>> +    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.
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