mirror of https://git.ffmpeg.org/ffmpeg.git
304 lines
9.9 KiB
C
304 lines
9.9 KiB
C
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/*
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* Copyright (c) 2023 Tomas Härdin
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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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/**
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* @file
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* MSRLE encoder
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* @see https://wiki.multimedia.cx/index.php?title=Microsoft_RLE
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*/
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// TODO: pal4 mode?
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#include "bytestream.h"
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#include "codec_internal.h"
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#include "encode.h"
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typedef struct MSRLEContext {
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const AVClass *class;
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int curframe;
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AVFrame *last_frame;
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} MSRLEContext;
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static av_cold int msrle_encode_init(AVCodecContext *avctx)
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{
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avctx->bits_per_coded_sample = 8;
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return 0;
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}
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static void write_run(AVCodecContext *avctx, uint8_t **data, int len, int value)
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{
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// we're allowed to write odd runs
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while (len >= 255) {
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bytestream_put_byte(data, 255);
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bytestream_put_byte(data, value);
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len -= 255;
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}
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if (len >= 1) {
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// this is wasteful when len == 1 and sometimes when len == 2
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// but sometimes we have no choice. also write_absolute()
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// relies on this
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bytestream_put_byte(data, len);
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bytestream_put_byte(data, value);
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}
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}
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static void write_absolute(AVCodecContext *avctx, uint8_t **data, uint8_t *line, int len)
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{
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// writing 255 would be wasteful here due to the padding requirement
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while (len >= 254) {
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bytestream_put_byte(data, 0);
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bytestream_put_byte(data, 254);
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bytestream_put_buffer(data, line, 254);
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line += 254;
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len -= 254;
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}
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if (len == 1) {
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// it's less wasteful to write single pixels as runs
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// not to mention that absolute mode requires >= 3 pixels
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write_run(avctx, data, 1, line[0]);
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} else if (len == 2) {
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write_run(avctx, data, 1, line[0]);
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write_run(avctx, data, 1, line[1]);
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} else if (len > 0) {
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bytestream_put_byte(data, 0);
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bytestream_put_byte(data, len);
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bytestream_put_buffer(data, line, len);
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if (len & 1)
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bytestream_put_byte(data, 0);
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}
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}
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static void write_delta(AVCodecContext *avctx, uint8_t **data, int delta)
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{
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// we let the yskip logic handle the case where we want to delta
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// to following lines. it's not perfect but it's easier than finding
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// the optimal combination of end-of-lines and deltas to reach any
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// following position including places where dx < 0
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while (delta >= 255) {
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bytestream_put_byte(data, 0);
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bytestream_put_byte(data, 2);
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bytestream_put_byte(data, 255);
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bytestream_put_byte(data, 0);
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delta -= 255;
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}
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if (delta > 0) {
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bytestream_put_byte(data, 0);
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bytestream_put_byte(data, 2);
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bytestream_put_byte(data, delta);
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bytestream_put_byte(data, 0);
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}
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}
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static void write_yskip(AVCodecContext *avctx, uint8_t **data, int yskip)
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{
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if (yskip < 4)
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return;
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// we have yskip*2 nul bytess
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*data -= 2*yskip;
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// the end-of-line counts as one skip
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yskip--;
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while (yskip >= 255) {
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bytestream_put_byte(data, 0);
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bytestream_put_byte(data, 2);
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bytestream_put_byte(data, 0);
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bytestream_put_byte(data, 255);
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yskip -= 255;
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}
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if (yskip > 0) {
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bytestream_put_byte(data, 0);
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bytestream_put_byte(data, 2);
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bytestream_put_byte(data, 0);
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bytestream_put_byte(data, yskip);
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}
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bytestream_put_be16(data, 0x0000);
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}
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// used both to encode lines in keyframes and to encode lines between deltas
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static void encode_line(AVCodecContext *avctx, uint8_t **data, uint8_t *line, int length)
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{
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int run = 0, last = -1, absstart = 0;
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if (length == 0)
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return;
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for (int x = 0; x < length; x++) {
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if (last == line[x]) {
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run++;
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if (run == 3)
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write_absolute(avctx, data, &line[absstart], x - absstart - 2);
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} else {
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if (run >= 3) {
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write_run(avctx, data, run, last);
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absstart = x;
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}
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run = 1;
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}
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last = line[x];
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}
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if (run >= 3)
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write_run(avctx, data, run, last);
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else
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write_absolute(avctx, data, &line[absstart], length - absstart);
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}
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static int encode(AVCodecContext *avctx, AVPacket *pkt,
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const AVFrame *pict, int keyframe, int *got_keyframe)
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{
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MSRLEContext *s = avctx->priv_data;
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uint8_t *data = pkt->data;
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/* Compare the current frame to the last frame, or code the entire frame
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if keyframe != 0. We're continually outputting pairs of bytes:
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00 00 end of line
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00 01 end of bitmap
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00 02 dx dy delta. move pointer to x+dx, y+dy
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00 ll dd dd .. absolute (verbatim) mode. ll >= 3
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rr dd run. rr >= 1
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For keyframes we only have absolute mode and runs at our disposal, and
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we are not allowed to end a line early. If this happens when keyframe == 0
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then *got_keyframe is set to 1 and s->curframe is reset.
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*/
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*got_keyframe = 1; // set to zero whenever we use a feature that makes this a not-keyframe
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if (keyframe) {
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for (int y = avctx->height-1; y >= 0; y--) {
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uint8_t *line = &pict->data[0][y*pict->linesize[0]];
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encode_line(avctx, &data, line, avctx->width);
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bytestream_put_be16(&data, 0x0000); // end of line
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}
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} else {
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// compare to previous frame
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int yskip = 0; // we can encode large skips using deltas
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for (int y = avctx->height-1; y >= 0; y--) {
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uint8_t *line = &pict->data[0][y*pict->linesize[0]];
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uint8_t *prev = &s->last_frame->data[0][y*s->last_frame->linesize[0]];
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// we need at least 5 pixels in a row for a delta to be worthwhile
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int delta = 0, linestart = 0, encoded = 0;
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for (int x = 0; x < avctx->width; x++) {
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if (line[x] == prev[x]) {
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delta++;
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if (delta == 5) {
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int len = x - linestart - 4;
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if (len > 0) {
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write_yskip(avctx, &data, yskip);
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yskip = 0;
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encode_line(avctx, &data, &line[linestart], len);
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encoded = 1;
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}
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linestart = -1;
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}
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} else {
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if (delta >= 5) {
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write_yskip(avctx, &data, yskip);
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yskip = 0;
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write_delta(avctx, &data, delta);
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*got_keyframe = 0;
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encoded = 1;
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}
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delta = 0;
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if (linestart == -1)
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linestart = x;
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}
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}
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if (delta < 5) {
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write_yskip(avctx, &data, yskip);
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yskip = 0;
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encode_line(avctx, &data, &line[linestart], avctx->width - linestart);
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encoded = 1;
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} else
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*got_keyframe = 0;
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bytestream_put_be16(&data, 0x0000); // end of line
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if (!encoded)
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yskip++;
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else
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yskip = 0;
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}
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write_yskip(avctx, &data, yskip);
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}
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bytestream_put_be16(&data, 0x0001); // end of bitmap
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pkt->size = data - pkt->data;
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return 0;
}
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static int msrle_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
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const AVFrame *pict, int *got_packet)
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{
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MSRLEContext *s = avctx->priv_data;
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int ret, got_keyframe;
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if ((ret = ff_alloc_packet(avctx, pkt, (
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avctx->width*2 /* worst case = rle every pixel */ + 2 /*end of line */
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) * avctx->height + 2 /* end of bitmap */ + AV_INPUT_BUFFER_MIN_SIZE)))
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return ret;
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if (pict->data[1]) {
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uint8_t *side_data = av_packet_new_side_data(pkt, AV_PKT_DATA_PALETTE, AVPALETTE_SIZE);
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memcpy(side_data, pict->data[1], AVPALETTE_SIZE);
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}
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if ((ret = encode(avctx, pkt, pict, s->curframe == 0, &got_keyframe)))
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return ret;
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if (got_keyframe) {
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pkt->flags |= AV_PKT_FLAG_KEY;
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s->curframe = 0;
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}
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if (++s->curframe >= avctx->gop_size)
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s->curframe = 0;
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*got_packet = 1;
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if (!s->last_frame)
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s->last_frame = av_frame_alloc();
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else
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av_frame_unref(s->last_frame);
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av_frame_ref(s->last_frame, pict);
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return 0;
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}
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static int msrle_encode_close(AVCodecContext *avctx)
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{
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MSRLEContext *s = avctx->priv_data;
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av_frame_free(&s->last_frame);
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return 0;
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}
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static const AVClass msrle_class = {
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.class_name = "Microsoft RLE encoder",
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.item_name = av_default_item_name,
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.version = LIBAVUTIL_VERSION_INT,
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};
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const FFCodec ff_msrle_encoder = {
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.p.name = "msrle",
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CODEC_LONG_NAME("Microsoft RLE"),
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.p.type = AVMEDIA_TYPE_VIDEO,
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.p.id = AV_CODEC_ID_MSRLE,
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.p.capabilities = AV_CODEC_CAP_DR1,
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.priv_data_size = sizeof(MSRLEContext),
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.init = msrle_encode_init,
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FF_CODEC_ENCODE_CB(msrle_encode_frame),
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.close = msrle_encode_close,
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.p.pix_fmts = (const enum AVPixelFormat[]){
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AV_PIX_FMT_PAL8, AV_PIX_FMT_NONE
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},
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.p.priv_class = &msrle_class,
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.caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
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};
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