FFmpeg: libavformat/mxg.c Source File

00001 /*
00002  * MxPEG clip file demuxer
00003  * Copyright (c) 2010 Anatoly Nenashev
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #include "libavutil/intreadwrite.h"
00023 #include "libavcodec/mjpeg.h"
00024 #include "avformat.h"
00025 #include "internal.h"
00026 #include "avio.h"
00027 
00028 #define DEFAULT_PACKET_SIZE 1024
00029 #define OVERREAD_SIZE 3
00030 
00031 typedef struct MXGContext {
00032     uint8_t *buffer;
00033     uint8_t *buffer_ptr;
00034     uint8_t *soi_ptr;
00035     unsigned int buffer_size;
00036     int64_t dts;
00037     unsigned int cache_size;
00038 } MXGContext;
00039 
00040 static int mxg_read_header(AVFormatContext *s, AVFormatParameters *ap)
00041 {
00042     AVStream *video_st, *audio_st;
00043     MXGContext *mxg = s->priv_data;
00044 
00045     /* video parameters will be extracted from the compressed bitstream */
00046     video_st = avformat_new_stream(s, NULL);
00047     if (!video_st)
00048         return AVERROR(ENOMEM);
00049     video_st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
00050     video_st->codec->codec_id = CODEC_ID_MXPEG;
00051     avpriv_set_pts_info(video_st, 64, 1, 1000000);
00052 
00053     audio_st = avformat_new_stream(s, NULL);
00054     if (!audio_st)
00055         return AVERROR(ENOMEM);
00056     audio_st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
00057     audio_st->codec->codec_id = CODEC_ID_PCM_ALAW;
00058     audio_st->codec->channels = 1;
00059     audio_st->codec->sample_rate = 8000;
00060     audio_st->codec->bits_per_coded_sample = 8;
00061     audio_st->codec->block_align = 1;
00062     avpriv_set_pts_info(audio_st, 64, 1, 1000000);
00063 
00064     mxg->soi_ptr = mxg->buffer_ptr = mxg->buffer = 0;
00065     mxg->buffer_size = 0;
00066     mxg->dts = AV_NOPTS_VALUE;
00067     mxg->cache_size = 0;
00068 
00069     return 0;
00070 }
00071 
00072 static uint8_t* mxg_find_startmarker(uint8_t *p, uint8_t *end)
00073 {
00074     for (; p < end - 3; p += 4) {
00075         uint32_t x = *(uint32_t*)p;
00076 
00077         if (x & (~(x+0x01010101)) & 0x80808080) {
00078             if (p[0] == 0xff) {
00079                 return p;
00080             } else if (p[1] == 0xff) {
00081                 return p+1;
00082             } else if (p[2] == 0xff) {
00083                 return p+2;
00084             } else if (p[3] == 0xff) {
00085                 return p+3;
00086             }
00087         }
00088     }
00089 
00090     for (; p < end; ++p) {
00091         if (*p == 0xff) return p;
00092     }
00093 
00094     return end;
00095 }
00096 
00097 static int mxg_update_cache(AVFormatContext *s, unsigned int cache_size)
00098 {
00099     MXGContext *mxg = s->priv_data;
00100     unsigned int current_pos = mxg->buffer_ptr - mxg->buffer;
00101     unsigned int soi_pos;
00102     int ret;
00103 
00104     /* reallocate internal buffer */
00105     if (current_pos > current_pos + cache_size)
00106         return AVERROR(ENOMEM);
00107     if (mxg->soi_ptr) soi_pos = mxg->soi_ptr - mxg->buffer;
00108     mxg->buffer = av_fast_realloc(mxg->buffer, &mxg->buffer_size,
00109                                   current_pos + cache_size +
00110                                   FF_INPUT_BUFFER_PADDING_SIZE);
00111     if (!mxg->buffer)
00112         return AVERROR(ENOMEM);
00113     mxg->buffer_ptr = mxg->buffer + current_pos;
00114     if (mxg->soi_ptr) mxg->soi_ptr = mxg->buffer + soi_pos;
00115 
00116     /* get data */
00117     ret = avio_read(s->pb, mxg->buffer_ptr + mxg->cache_size,
00118                      cache_size - mxg->cache_size);
00119     if (ret < 0)
00120         return ret;
00121 
00122     mxg->cache_size += ret;
00123 
00124     return ret;
00125 }
00126 
00127 static int mxg_read_packet(AVFormatContext *s, AVPacket *pkt)
00128 {
00129     int ret;
00130     unsigned int size;
00131     uint8_t *startmarker_ptr, *end, *search_end, marker;
00132     MXGContext *mxg = s->priv_data;
00133 
00134     while (!url_feof(s->pb) && !s->pb->error){
00135         if (mxg->cache_size <= OVERREAD_SIZE) {
00136             /* update internal buffer */
00137             ret = mxg_update_cache(s, DEFAULT_PACKET_SIZE + OVERREAD_SIZE);
00138             if (ret < 0)
00139                 return ret;
00140         }
00141         end = mxg->buffer_ptr + mxg->cache_size;
00142 
00143         /* find start marker - 0xff */
00144         if (mxg->cache_size > OVERREAD_SIZE) {
00145             search_end = end - OVERREAD_SIZE;
00146             startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);
00147         } else {
00148             search_end = end;
00149             startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);
00150             if (startmarker_ptr >= search_end - 1 ||
00151                 *(startmarker_ptr + 1) != EOI) break;
00152         }
00153 
00154         if (startmarker_ptr != search_end) { /* start marker found */
00155             marker = *(startmarker_ptr + 1);
00156             mxg->buffer_ptr = startmarker_ptr + 2;
00157             mxg->cache_size = end - mxg->buffer_ptr;
00158 
00159             if (marker == SOI) {
00160                 mxg->soi_ptr = startmarker_ptr;
00161             } else if (marker == EOI) {
00162                 if (!mxg->soi_ptr) {
00163                     av_log(s, AV_LOG_WARNING, "Found EOI before SOI, skipping\n");
00164                     continue;
00165                 }
00166 
00167                 pkt->pts = pkt->dts = mxg->dts;
00168                 pkt->stream_index = 0;
00169                 pkt->destruct = NULL;
00170                 pkt->size = mxg->buffer_ptr - mxg->soi_ptr;
00171                 pkt->data = mxg->soi_ptr;
00172 
00173                 if (mxg->soi_ptr - mxg->buffer > mxg->cache_size) {
00174                     if (mxg->cache_size > 0) {
00175                         memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);
00176                     }
00177 
00178                     mxg->buffer_ptr = mxg->buffer;
00179                 }
00180                 mxg->soi_ptr = 0;
00181 
00182                 return pkt->size;
00183             } else if ( (SOF0 <= marker && marker <= SOF15) ||
00184                         (SOS  <= marker && marker <= COM) ) {
00185                 /* all other markers that start marker segment also contain
00186                    length value (see specification for JPEG Annex B.1) */
00187                 size = AV_RB16(mxg->buffer_ptr);
00188                 if (size < 2)
00189                     return AVERROR(EINVAL);
00190 
00191                 if (mxg->cache_size < size) {
00192                     ret = mxg_update_cache(s, size);
00193                     if (ret < 0)
00194                         return ret;
00195                     startmarker_ptr = mxg->buffer_ptr - 2;
00196                     mxg->cache_size = 0;
00197                 } else {
00198                     mxg->cache_size -= size;
00199                 }
00200 
00201                 mxg->buffer_ptr += size;
00202 
00203                 if (marker == APP13 && size >= 16) { /* audio data */
00204                     /* time (GMT) of first sample in usec since 1970, little-endian */
00205                     pkt->pts = pkt->dts = AV_RL64(startmarker_ptr + 8);
00206                     pkt->stream_index = 1;
00207                     pkt->destruct = NULL;
00208                     pkt->size = size - 14;
00209                     pkt->data = startmarker_ptr + 16;
00210 
00211                     if (startmarker_ptr - mxg->buffer > mxg->cache_size) {
00212                         if (mxg->cache_size > 0) {
00213                             memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);
00214                         }
00215                         mxg->buffer_ptr = mxg->buffer;
00216                     }
00217 
00218                     return pkt->size;
00219                 } else if (marker == COM && size >= 18 &&
00220                            !strncmp(startmarker_ptr + 4, "MXF", 3)) {
00221                     /* time (GMT) of video frame in usec since 1970, little-endian */
00222                     mxg->dts = AV_RL64(startmarker_ptr + 12);
00223                 }
00224             }
00225         } else {
00226             /* start marker not found */
00227             mxg->buffer_ptr = search_end;
00228             mxg->cache_size = OVERREAD_SIZE;
00229         }
00230     }
00231 
00232     return AVERROR_EOF;
00233 }
00234 
00235 static int mxg_close(struct AVFormatContext *s)
00236 {
00237     MXGContext *mxg = s->priv_data;
00238     av_freep(&mxg->buffer);
00239     return 0;
00240 }
00241 
00242 AVInputFormat ff_mxg_demuxer = {
00243     .name = "mxg",
00244     .long_name = NULL_IF_CONFIG_SMALL("MxPEG clip file format"),
00245     .priv_data_size = sizeof(MXGContext),
00246     .read_header = mxg_read_header,
00247     .read_packet = mxg_read_packet,
00248     .read_close = mxg_close,
00249     .extensions = "mxg"
00250 };