FFmpeg/libavcodec/flashsvenc.c

/*
 * Flash Screen Video encoder
 * Copyright (C) 2004 Alex Beregszaszi
 * Copyright (C) 2006 Benjamin Larsson
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/* Encoding development sponsored by http://fh-campuswien.ac.at */

/**
 * @file
 * Flash Screen Video encoder
 * @author Alex Beregszaszi
 * @author Benjamin Larsson
 */

/* Bitstream description
 * The picture is divided into blocks that are zlib-compressed.
 *
 * The decoder is fed complete frames, the frameheader contains:
 *  4 bits of block width
 * 12 bits of frame width
 *  4 bits of block height
 * 12 bits of frame height
 *
 * Directly after the header are the compressed blocks. The blocks
 * have their compressed size represented with 16 bits in the beginning.
 * If the size = 0 then the block is unchanged from the previous frame.
 * All blocks are decompressed until the buffer is consumed.
 *
 * Encoding ideas: A basic encoder would just use a fixed block size.
 * Block sizes can be multiples of 16, from 16 to 256. The blocks don't
 * have to be quadratic. A brute force search with a set of different
 * block sizes should give a better result than to just use a fixed size.
 *
 * TODO:
 * Don't reencode the frame in brute force mode if the frame is a dupe.
 * Speed up. Make the difference check faster.
 */

#include <stdio.h>
#include <stdlib.h>
#include <zlib.h>

#include "avcodec.h"
#include "put_bits.h"
#include "bytestream.h"


typedef struct FlashSVContext {
    AVCodecContext *avctx;
    uint8_t        *previous_frame;
    AVFrame         frame;
    int             image_width, image_height;
    int             block_width, block_height;
    uint8_t        *tmpblock;
    uint8_t        *encbuffer;
    int             block_size;
    z_stream        zstream;
    int             last_key_frame;
} FlashSVContext;

static int copy_region_enc(uint8_t *sptr, uint8_t *dptr, int dx, int dy,
                           int h, int w, int stride, uint8_t *pfptr)
{
    int i, j;
    uint8_t *nsptr;
    uint8_t *npfptr;
    int diff = 0;

    for (i = dx + h; i > dx; i--) {
        nsptr  = sptr  + i * stride + dy * 3;
        npfptr = pfptr + i * stride + dy * 3;
        for (j = 0; j < w * 3; j++) {
            diff    |= npfptr[j] ^ nsptr[j];
            dptr[j]  = nsptr[j];
        }
        dptr += w * 3;
    }
    if (diff)
        return 1;
    return 0;
}

static av_cold int flashsv_encode_init(AVCodecContext *avctx)
{
    FlashSVContext *s = avctx->priv_data;

    s->avctx = avctx;

    if (avctx->width > 4095 || avctx->height > 4095) {
        av_log(avctx, AV_LOG_ERROR,
               "Input dimensions too large, input must be max 4096x4096 !\n");
        return AVERROR_INVALIDDATA;
    }

    // Needed if zlib unused or init aborted before deflateInit
    memset(&s->zstream, 0, sizeof(z_stream));

    s->last_key_frame = 0;

    s->image_width  = avctx->width;
    s->image_height = avctx->height;

    s->tmpblock  = av_mallocz(3 * 256 * 256);
    s->encbuffer = av_mallocz(s->image_width * s->image_height * 3);

    if (!s->tmpblock || !s->encbuffer) {
        av_log(avctx, AV_LOG_ERROR, "Memory allocation failed.\n");
        return AVERROR(ENOMEM);
    }

    return 0;
}


static int encode_bitstream(FlashSVContext *s, AVFrame *p, uint8_t *buf,
                            int buf_size, int block_width, int block_height,
                            uint8_t *previous_frame, int *I_frame)
{

    PutBitContext pb;
    int h_blocks, v_blocks, h_part, v_part, i, j;
    int buf_pos, res;
    int pred_blocks = 0;

    init_put_bits(&pb, buf, buf_size * 8);

    put_bits(&pb,  4, block_width / 16 - 1);
    put_bits(&pb, 12, s->image_width);
    put_bits(&pb,  4, block_height / 16 - 1);
    put_bits(&pb, 12, s->image_height);
    flush_put_bits(&pb);
    buf_pos = 4;

    h_blocks = s->image_width  / block_width;
    h_part   = s->image_width  % block_width;
    v_blocks = s->image_height / block_height;
    v_part   = s->image_height % block_height;

    /* loop over all block columns */
    for (j = 0; j < v_blocks + (v_part ? 1 : 0); j++) {

        int hp = j * block_height; // horizontal position in frame
        int hs = (j < v_blocks) ? block_height : v_part; // size of block

        /* loop over all block rows */
        for (i = 0; i < h_blocks + (h_part ? 1 : 0); i++) {
            int wp  = i * block_width; // vertical position in frame
            int ws  = (i < h_blocks) ? block_width : h_part; // size of block
            int ret = Z_OK;
            uint8_t *ptr = buf + buf_pos;

            /* copy the block to the temp buffer before compression
             * (if it differs from the previous frame's block) */
            res = copy_region_enc(p->data[0], s->tmpblock,
                                  s->image_height - (hp + hs + 1),
                                  wp, hs, ws, p->linesize[0], previous_frame);

            if (res || *I_frame) {
                unsigned long zsize = 3 * block_width * block_height;
                ret   = compress2(ptr + 2, &zsize, s->tmpblock, 3 * ws * hs, 9);

                //ret = deflateReset(&s->zstream);
                if (ret != Z_OK)
                    av_log(s->avctx, AV_LOG_ERROR,
                           "error while compressing block %dx%d\n", i, j);

                bytestream_put_be16(&ptr, (unsigned int) zsize);
                buf_pos += zsize + 2;
                av_dlog(avctx, "buf_pos = %d\n", buf_pos);
            } else {
                pred_blocks++;
                bytestream_put_be16(&ptr, 0);
                buf_pos += 2;
            }
        }
    }

    if (pred_blocks)
        *I_frame = 0;
    else
        *I_frame = 1;

    return buf_pos;
}


static int flashsv_encode_frame(AVCodecContext *avctx, uint8_t *buf,
                                int buf_size, void *data)
{
    FlashSVContext * const s = avctx->priv_data;
    AVFrame *pict = data;
    AVFrame * const p = &s->frame;
    uint8_t *pfptr;
    int res;
    int I_frame = 0;
    int opt_w = 4, opt_h = 4;

    *p = *pict;

    /* First frame needs to be a keyframe */
    if (avctx->frame_number == 0) {
        s->previous_frame = av_mallocz(FFABS(p->linesize[0]) * s->image_height);
        if (!s->previous_frame) {
            av_log(avctx, AV_LOG_ERROR, "Memory allocation failed.\n");
            return AVERROR(ENOMEM);
        }
        I_frame = 1;
    }

    if (p->linesize[0] < 0)
        pfptr = s->previous_frame - (s->image_height - 1) * p->linesize[0];
    else
        pfptr = s->previous_frame;

    /* Check the placement of keyframes */
    if (avctx->gop_size > 0 &&
        avctx->frame_number >= s->last_key_frame + avctx->gop_size) {
        I_frame = 1;
    }

    if (buf_size < s->image_width * s->image_height * 3) {
        //Conservative upper bound check for compressed data
        av_log(avctx, AV_LOG_ERROR, "buf_size %d <  %d\n",
               buf_size, s->image_width * s->image_height * 3);
        return -1;
    }

    res = encode_bitstream(s, p, buf, buf_size, opt_w * 16, opt_h * 16,
                           pfptr, &I_frame);

    //save the current frame
    if (p->linesize[0] > 0)
        memcpy(s->previous_frame, p->data[0], s->image_height * p->linesize[0]);
    else
        memcpy(s->previous_frame,
               p->data[0] + p->linesize[0] * (s->image_height - 1),
               s->image_height * FFABS(p->linesize[0]));

    //mark the frame type so the muxer can mux it correctly
    if (I_frame) {
        p->pict_type      = AV_PICTURE_TYPE_I;
        p->key_frame      = 1;
        s->last_key_frame = avctx->frame_number;
        av_dlog(avctx, "Inserting keyframe at frame %d\n", avctx->frame_number);
    } else {
        p->pict_type = AV_PICTURE_TYPE_P;
        p->key_frame = 0;
    }

    avctx->coded_frame = p;

    return res;
}

static av_cold int flashsv_encode_end(AVCodecContext *avctx)
{
    FlashSVContext *s = avctx->priv_data;

    deflateEnd(&s->zstream);

    av_free(s->encbuffer);
    av_free(s->previous_frame);
    av_free(s->tmpblock);

    return 0;
}

AVCodec ff_flashsv_encoder = {
    .name           = "flashsv",
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = CODEC_ID_FLASHSV,
    .priv_data_size = sizeof(FlashSVContext),
    .init           = flashsv_encode_init,
    .encode         = flashsv_encode_frame,
    .close          = flashsv_encode_end,
    .pix_fmts       = (const enum PixelFormat[]){PIX_FMT_BGR24, PIX_FMT_NONE},
    .long_name      = NULL_IF_CONFIG_SMALL("Flash Screen Video"),
};