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ffmpeg / libavformat / a64.c @ 133cc989

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/*
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 * a64 muxer
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 * Copyright (c) 2009 Tobias Bindhammer
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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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#include "libavcodec/avcodec.h"
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#include "libavcodec/a64enc.h"
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#include "libavcodec/bytestream.h"
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#include "avformat.h"
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typedef struct A64MuxerContext {
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    int interleaved;
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    AVPacket prev_pkt;
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    int prev_frame_count;
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} A64MuxerContext;
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static int a64_write_header(struct AVFormatContext *s)
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{
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    AVCodecContext *avctx = s->streams[0]->codec;
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    A64MuxerContext *c = s->priv_data;
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    uint8_t header[5] = {
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        0x00, //load
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        0x40, //address
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        0x00, //mode
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        0x00, //charset_lifetime (multi only)
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        0x00  //fps in 50/fps;
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    };
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    c->interleaved = 0;
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    switch (avctx->codec->id) {
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    case CODEC_ID_A64_MULTI:
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        header[2] = 0x00;
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        header[3] = AV_RB32(avctx->extradata+0);
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        header[4] = 2;
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        break;
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    case CODEC_ID_A64_MULTI5:
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        header[2] = 0x01;
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        header[3] = AV_RB32(avctx->extradata+0);
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        header[4] = 3;
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        break;
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    default:
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        return AVERROR(EINVAL);
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        break;
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    }
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    put_buffer(s->pb, header, 2);
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    c->prev_pkt.size = 0;
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    c->prev_frame_count = 0;
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    return 0;
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}
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static int a64_write_packet(struct AVFormatContext *s, AVPacket *pkt)
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{
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    AVCodecContext *avctx = s->streams[0]->codec;
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    A64MuxerContext *c = s->priv_data;
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    int i, j;
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    int ch_chunksize;
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    int lifetime;
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    int frame_count;
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    int charset_size;
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    int frame_size;
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    int num_frames;
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    /* fetch values from extradata */
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    switch (avctx->codec->id) {
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    case CODEC_ID_A64_MULTI:
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    case CODEC_ID_A64_MULTI5:
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        if(c->interleaved) {
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            /* Write interleaved, means we insert chunks of the future charset before each current frame.
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             * Reason: if we load 1 charset + corresponding frames in one block on c64, we need to store
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             * them first and then display frame by frame to keep in sync. Thus we would read and write
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             * the data for colram from/to ram first and waste too much time. If we interleave and send the
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             * charset beforehand, we assemble a new charset chunk by chunk, write current screen data to
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             * screen-ram to be displayed and decode the colram directly to colram-location $d800 during
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             * the overscan, while reading directly from source
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             * This is the only way so far, to achieve 25fps on c64 */
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            if(avctx->extradata) {
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                /* fetch values from extradata */
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                lifetime     = AV_RB32(avctx->extradata + 0);
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                frame_count  = AV_RB32(avctx->extradata + 4);
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                charset_size = AV_RB32(avctx->extradata + 8);
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                frame_size   = AV_RB32(avctx->extradata + 12);
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                /* TODO: sanity checks? */
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            }
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            else {
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                av_log(avctx, AV_LOG_ERROR, "extradata not set\n");
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                return AVERROR(EINVAL);
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            }
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            ch_chunksize=charset_size/lifetime;
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            /* TODO: check if charset/size is % lifetime, but maybe check in codec */
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            if(pkt->data) num_frames = lifetime;
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            else num_frames = c->prev_frame_count;
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            for(i = 0; i < num_frames; i++) {
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                if(pkt->data) {
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                    /* if available, put newest charset chunk into buffer */
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                    put_buffer(s->pb, pkt->data + ch_chunksize * i, ch_chunksize);
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                }
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                else {
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                    /* a bit ugly, but is there an alternative to put many zeros? */
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                    for(j = 0; j < ch_chunksize; j++) put_byte(s->pb, 0);
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                }
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                if(c->prev_pkt.data) {
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                    /* put frame (screen + colram) from last packet into buffer */
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                    put_buffer(s->pb, c->prev_pkt.data + charset_size + frame_size * i, frame_size);
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                }
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                else {
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                    /* a bit ugly, but is there an alternative to put many zeros? */
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                    for(j = 0; j < frame_size; j++) put_byte(s->pb, 0);
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                }
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            }
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            /* backup current packet for next turn */
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            if(pkt->data) {
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                av_new_packet(&c->prev_pkt, pkt->size);
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                memcpy(c->prev_pkt.data, pkt->data, pkt->size);
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            }
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            c->prev_frame_count = frame_count;
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            break;
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        }
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        default:
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            /* Write things as is. Nice for self-contained frames from non-multicolor modes or if played
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             * directly from ram and not from a streaming device (rrnet/mmc) */
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            if(pkt) put_buffer(s->pb, pkt->data, pkt->size);
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        break;
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    }
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    put_flush_packet(s->pb);
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    return 0;
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}
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static int a64_write_trailer(struct AVFormatContext *s)
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{
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    A64MuxerContext *c = s->priv_data;
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    AVPacket pkt;
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    /* need to flush last packet? */
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    if(c->interleaved) a64_write_packet(s, &pkt);
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    return 0;
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}
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AVOutputFormat a64_muxer = {
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    .name = "a64",
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    .long_name = NULL_IF_CONFIG_SMALL("a64 - video for Commodore 64"),
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    .mime_type = NULL,
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    .extensions = "a64, A64",
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    .priv_data_size = sizeof (A64Context),
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    .video_codec = CODEC_ID_A64_MULTI,
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    a64_write_header,
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    a64_write_packet,
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    a64_write_trailer
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};