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ffmpeg / libavcodec / flashsvenc.c @ ce5e49b0

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/*
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 * Flash Screen Video encoder
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 * Copyright (C) 2004 Alex Beregszaszi
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 * Copyright (C) 2006 Benjamin Larsson
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/* Encoding development sponsored by http://fh-campuswien.ac.at */
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/**
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 * @file
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 * Flash Screen Video encoder
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 * @author Alex Beregszaszi
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 * @author Benjamin Larsson
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 */
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/* Bitstream description
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 * The picture is divided into blocks that are zlib-compressed.
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 *
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 * The decoder is fed complete frames, the frameheader contains:
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 * 4bits of block width
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 * 12bits of frame width
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 * 4bits of block height
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 * 12bits of frame height
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 *
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 * Directly after the header are the compressed blocks. The blocks
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 * have their compressed size represented with 16bits in the beginig.
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 * If the size = 0 then the block is unchanged from the previous frame.
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 * All blocks are decompressed until the buffer is consumed.
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 *
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 * Encoding ideas, a basic encoder would just use a fixed block size.
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 * Block sizes can be multipels of 16, from 16 to 256. The blocks don't
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 * have to be quadratic. A brute force search with a set of different
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 * block sizes should give a better result than to just use a fixed size.
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 */
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/* TODO:
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 * Don't reencode the frame in brute force mode if the frame is a dupe. Speed up.
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 * Make the difference check faster.
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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <zlib.h>
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#include "avcodec.h"
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#include "put_bits.h"
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#include "bytestream.h"
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typedef struct FlashSVContext {
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    AVCodecContext *avctx;
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    uint8_t        *previous_frame;
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    AVFrame         frame;
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    int             image_width, image_height;
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    int             block_width, block_height;
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    uint8_t        *tmpblock;
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    uint8_t        *encbuffer;
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    int             block_size;
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    z_stream        zstream;
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    int             last_key_frame;
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} FlashSVContext;
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static int copy_region_enc(uint8_t *sptr, uint8_t *dptr, int dx, int dy,
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                           int h, int w, int stride, uint8_t *pfptr)
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{
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    int i, j;
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    uint8_t *nsptr;
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    uint8_t *npfptr;
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    int diff = 0;
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    for (i = dx + h; i > dx; i--) {
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        nsptr  = sptr  + (i * stride) + dy * 3;
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        npfptr = pfptr + (i * stride) + dy * 3;
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        for (j = 0; j < w * 3; j++) {
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            diff    |= npfptr[j] ^ nsptr[j];
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            dptr[j]  = nsptr[j];
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        }
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        dptr += w * 3;
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    }
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    if (diff)
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        return 1;
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    return 0;
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}
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static av_cold int flashsv_encode_init(AVCodecContext *avctx)
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{
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    FlashSVContext *s = avctx->priv_data;
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    s->avctx = avctx;
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    if ((avctx->width > 4095) || (avctx->height > 4095)) {
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        av_log(avctx, AV_LOG_ERROR, "Input dimensions too large, input must be max 4096x4096 !\n");
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        return AVERROR_INVALIDDATA;
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    }
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    // Needed if zlib unused or init aborted before deflateInit
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    memset(&(s->zstream), 0, sizeof(z_stream));
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    s->last_key_frame = 0;
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    s->image_width  = avctx->width;
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    s->image_height = avctx->height;
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    s->tmpblock  = av_mallocz(3 * 256 * 256);
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    s->encbuffer = av_mallocz(s->image_width * s->image_height * 3);
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    if (!s->tmpblock || !s->encbuffer) {
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        av_log(avctx, AV_LOG_ERROR, "Memory allocation failed.\n");
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        return AVERROR(ENOMEM);
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    }
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    return 0;
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}
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static int encode_bitstream(FlashSVContext *s, AVFrame *p, uint8_t *buf,
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                            int buf_size, int block_width, int block_height,
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                            uint8_t *previous_frame, int *I_frame)
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{
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    PutBitContext pb;
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    int h_blocks, v_blocks, h_part, v_part, i, j;
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    int buf_pos, res;
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    int pred_blocks = 0;
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    init_put_bits(&pb, buf, buf_size * 8);
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    put_bits(&pb,  4, (block_width / 16) - 1);
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    put_bits(&pb, 12, s->image_width);
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    put_bits(&pb,  4, (block_height / 16) - 1);
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    put_bits(&pb, 12, s->image_height);
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    flush_put_bits(&pb);
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    buf_pos = 4;
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    h_blocks = s->image_width  / block_width;
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    h_part   = s->image_width  % block_width;
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    v_blocks = s->image_height / block_height;
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    v_part   = s->image_height % block_height;
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    /* loop over all block columns */
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    for (j = 0; j < v_blocks + (v_part ? 1 : 0); j++) {
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        int hp = j * block_height; // horiz position in frame
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        int hs = (j < v_blocks) ? block_height : v_part; // size of block
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        /* loop over all block rows */
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        for (i = 0; i < h_blocks + (h_part ? 1 : 0); i++) {
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            int wp  = i * block_width; // vert position in frame
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            int ws  = (i < h_blocks) ? block_width : h_part; // size of block
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            int ret = Z_OK;
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            uint8_t *ptr;
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            ptr = buf + buf_pos;
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            /* copy the block to the temp buffer before compression
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             * (if it differs from the previous frame's block) */
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            res = copy_region_enc(p->data[0], s->tmpblock,
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                                  s->image_height - (hp + hs + 1),
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                                  wp, hs, ws, p->linesize[0], previous_frame);
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            if (res || *I_frame) {
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                unsigned long zsize;
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                zsize = 3 * block_width * block_height;
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                ret   = compress2(ptr + 2, &zsize, s->tmpblock, 3 * ws * hs, 9);
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                //ret = deflateReset(&(s->zstream));
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                if (ret != Z_OK)
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                    av_log(s->avctx, AV_LOG_ERROR, "error while compressing block %dx%d\n", i, j);
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                bytestream_put_be16(&ptr, (unsigned int) zsize);
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                buf_pos += zsize + 2;
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                //av_log(avctx, AV_LOG_ERROR, "buf_pos = %d\n", buf_pos);
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            } else {
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                pred_blocks++;
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                bytestream_put_be16(&ptr, 0);
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                buf_pos += 2;
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            }
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        }
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    }
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    if (pred_blocks)
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        *I_frame = 0;
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    else
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        *I_frame = 1;
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    return buf_pos;
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}
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static int flashsv_encode_frame(AVCodecContext *avctx, uint8_t *buf,
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                                int buf_size, void *data)
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{
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    FlashSVContext * const s = avctx->priv_data;
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    AVFrame *pict = data;
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    AVFrame * const p = &s->frame;
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    uint8_t *pfptr;
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    int res;
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    int I_frame = 0;
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    int opt_w, opt_h;
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    *p = *pict;
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    /* First frame needs to be a keyframe */
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    if (avctx->frame_number == 0) {
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        s->previous_frame = av_mallocz(FFABS(p->linesize[0]) * s->image_height);
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        if (!s->previous_frame) {
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            av_log(avctx, AV_LOG_ERROR, "Memory allocation failed.\n");
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            return AVERROR(ENOMEM);
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        }
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        I_frame = 1;
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    }
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    if (p->linesize[0] < 0)
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        pfptr = s->previous_frame - ((s->image_height - 1) * p->linesize[0]);
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    else
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        pfptr = s->previous_frame;
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    /* Check the placement of keyframes */
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    if (avctx->gop_size > 0) {
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        if (avctx->frame_number >= s->last_key_frame + avctx->gop_size) {
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            I_frame = 1;
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        }
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    }
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    opt_w = 4;
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    opt_h = 4;
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    if (buf_size < s->image_width*s->image_height*3) {
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        //Conservative upper bound check for compressed data
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        av_log(avctx, AV_LOG_ERROR, "buf_size %d <  %d\n",
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               buf_size, s->image_width * s->image_height * 3);
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        return -1;
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    }
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    res = encode_bitstream(s, p, buf, buf_size, opt_w * 16, opt_h * 16, pfptr, &I_frame);
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    //save the current frame
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    if (p->linesize[0] > 0)
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        memcpy(s->previous_frame, p->data[0], s->image_height * p->linesize[0]);
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    else
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        memcpy(s->previous_frame, p->data[0] + p->linesize[0] * (s->image_height - 1),
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               s->image_height * FFABS(p->linesize[0]));
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    //mark the frame type so the muxer can mux it correctly
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    if (I_frame) {
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        p->pict_type = AV_PICTURE_TYPE_I;
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        p->key_frame = 1;
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        s->last_key_frame = avctx->frame_number;
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        av_log(avctx, AV_LOG_DEBUG, "Inserting key frame at frame %d\n", avctx->frame_number);
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    } else {
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        p->pict_type = AV_PICTURE_TYPE_P;
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        p->key_frame = 0;
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    }
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    avctx->coded_frame = p;
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    return res;
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}
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static av_cold int flashsv_encode_end(AVCodecContext *avctx)
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{
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    FlashSVContext *s = avctx->priv_data;
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    deflateEnd(&(s->zstream));
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    av_free(s->encbuffer);
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    av_free(s->previous_frame);
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    av_free(s->tmpblock);
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    return 0;
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}
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AVCodec ff_flashsv_encoder = {
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    .name           = "flashsv",
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    .type           = AVMEDIA_TYPE_VIDEO,
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    .id             = CODEC_ID_FLASHSV,
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    .priv_data_size = sizeof(FlashSVContext),
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    .init           = flashsv_encode_init,
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    .encode         = flashsv_encode_frame,
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    .close          = flashsv_encode_end,
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    .pix_fmts       = (const enum PixelFormat[]){PIX_FMT_BGR24, PIX_FMT_NONE},
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    .long_name      = NULL_IF_CONFIG_SMALL("Flash Screen Video"),
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};
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