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 "avio.h"
00026 
00027 #define VIDEO_STREAM_INDEX 0
00028 #define AUDIO_STREAM_INDEX 1
00029 #define DEFAULT_PACKET_SIZE 1024
00030 #define OVERREAD_SIZE 3
00031 
00032 typedef struct MXGContext {
00033     uint8_t *buffer;
00034     uint8_t *buffer_ptr;
00035     uint8_t *soi_ptr;
00036     unsigned int buffer_size;
00037     int64_t dts;
00038     unsigned int cache_size;
00039 } MXGContext;
00040 
00041 static int mxg_read_header(AVFormatContext *s, AVFormatParameters *ap)
00042 {
00043     AVStream *video_st, *audio_st;
00044     MXGContext *mxg = s->priv_data;
00045 
00046     /* video parameters will be extracted from the compressed bitstream */
00047     video_st = av_new_stream(s, VIDEO_STREAM_INDEX);
00048     if (!video_st)
00049         return AVERROR(ENOMEM);
00050     video_st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
00051     video_st->codec->codec_id = CODEC_ID_MXPEG;
00052     av_set_pts_info(video_st, 64, 1, 1000000);
00053 
00054     audio_st = av_new_stream(s, AUDIO_STREAM_INDEX);
00055     if (!audio_st)
00056         return AVERROR(ENOMEM);
00057     audio_st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
00058     audio_st->codec->codec_id = CODEC_ID_PCM_ALAW;
00059     audio_st->codec->channels = 1;
00060     audio_st->codec->sample_rate = 8000;
00061     audio_st->codec->bits_per_coded_sample = 8;
00062     audio_st->codec->block_align = 1;
00063     av_set_pts_info(audio_st, 64, 1, 1000000);
00064 
00065     mxg->soi_ptr = mxg->buffer_ptr = mxg->buffer = 0;
00066     mxg->buffer_size = 0;
00067     mxg->dts = AV_NOPTS_VALUE;
00068     mxg->cache_size = 0;
00069 
00070     return 0;
00071 }
00072 
00073 static uint8_t* mxg_find_startmarker(uint8_t *p, uint8_t *end)
00074 {
00075     for (; p < end - 3; p += 4) {
00076         uint32_t x = *(uint32_t*)p;
00077 
00078         if (x & (~(x+0x01010101)) & 0x80808080) {
00079             if (p[0] == 0xff) {
00080                 return p;
00081             } else if (p[1] == 0xff) {
00082                 return p+1;
00083             } else if (p[2] == 0xff) {
00084                 return p+2;
00085             } else if (p[3] == 0xff) {
00086                 return p+3;
00087             }
00088         }
00089     }
00090 
00091     for (; p < end; ++p) {
00092         if (*p == 0xff) return p;
00093     }
00094 
00095     return end;
00096 }
00097 
00098 static int mxg_update_cache(AVFormatContext *s, unsigned int cache_size)
00099 {
00100     MXGContext *mxg = s->priv_data;
00101     unsigned int current_pos = mxg->buffer_ptr - mxg->buffer;
00102     unsigned int soi_pos;
00103     int ret;
00104 
00105     /* reallocate internal buffer */
00106     if (current_pos > current_pos + cache_size)
00107         return AVERROR(ENOMEM);
00108     if (mxg->soi_ptr) soi_pos = mxg->soi_ptr - mxg->buffer;
00109     mxg->buffer = av_fast_realloc(mxg->buffer, &mxg->buffer_size,
00110                                   current_pos + cache_size +
00111                                   FF_INPUT_BUFFER_PADDING_SIZE);
00112     if (!mxg->buffer)
00113         return AVERROR(ENOMEM);
00114     mxg->buffer_ptr = mxg->buffer + current_pos;
00115     if (mxg->soi_ptr) mxg->soi_ptr = mxg->buffer + soi_pos;
00116 
00117     /* get data */
00118     ret = avio_read(s->pb, mxg->buffer_ptr + mxg->cache_size,
00119                      cache_size - mxg->cache_size);
00120     if (ret < 0)
00121         return ret;
00122 
00123     mxg->cache_size += ret;
00124 
00125     return ret;
00126 }
00127 
00128 static int mxg_read_packet(AVFormatContext *s, AVPacket *pkt)
00129 {
00130     int ret;
00131     unsigned int size;
00132     uint8_t *startmarker_ptr, *end, *search_end, marker;
00133     MXGContext *mxg = s->priv_data;
00134 
00135     while (!url_feof(s->pb) && !s->pb->error){
00136         if (mxg->cache_size <= OVERREAD_SIZE) {
00137             /* update internal buffer */
00138             ret = mxg_update_cache(s, DEFAULT_PACKET_SIZE + OVERREAD_SIZE);
00139             if (ret < 0)
00140                 return ret;
00141         }
00142         end = mxg->buffer_ptr + mxg->cache_size;
00143 
00144         /* find start marker - 0xff */
00145         if (mxg->cache_size > OVERREAD_SIZE) {
00146             search_end = end - OVERREAD_SIZE;
00147             startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);
00148         } else {
00149             search_end = end;
00150             startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);
00151             if (startmarker_ptr >= search_end - 1 ||
00152                 *(startmarker_ptr + 1) != EOI) break;
00153         }
00154 
00155         if (startmarker_ptr != search_end) { /* start marker found */
00156             marker = *(startmarker_ptr + 1);
00157             mxg->buffer_ptr = startmarker_ptr + 2;
00158             mxg->cache_size = end - mxg->buffer_ptr;
00159 
00160             if (marker == SOI) {
00161                 mxg->soi_ptr = startmarker_ptr;
00162             } else if (marker == EOI) {
00163                 if (!mxg->soi_ptr) {
00164                     av_log(s, AV_LOG_WARNING, "Found EOI before SOI, skipping\n");
00165                     continue;
00166                 }
00167 
00168                 pkt->pts = pkt->dts = mxg->dts;
00169                 pkt->stream_index = VIDEO_STREAM_INDEX;
00170                 pkt->destruct = NULL;
00171                 pkt->size = mxg->buffer_ptr - mxg->soi_ptr;
00172                 pkt->data = mxg->soi_ptr;
00173 
00174                 if (mxg->soi_ptr - mxg->buffer > mxg->cache_size) {
00175                     if (mxg->cache_size > 0) {
00176                         memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);
00177                     }
00178 
00179                     mxg->buffer_ptr = mxg->buffer;
00180                 }
00181                 mxg->soi_ptr = 0;
00182 
00183                 return pkt->size;
00184             } else if ( (SOF0 <= marker && marker <= SOF15) ||
00185                         (SOS  <= marker && marker <= COM) ) {
00186                 /* all other markers that start marker segment also contain
00187                    length value (see specification for JPEG Annex B.1) */
00188                 size = AV_RB16(mxg->buffer_ptr);
00189                 if (size < 2)
00190                     return AVERROR(EINVAL);
00191 
00192                 if (mxg->cache_size < size) {
00193                     ret = mxg_update_cache(s, size);
00194                     if (ret < 0)
00195                         return ret;
00196                     startmarker_ptr = mxg->buffer_ptr - 2;
00197                     mxg->cache_size = 0;
00198                 } else {
00199                     mxg->cache_size -= size;
00200                 }
00201 
00202                 mxg->buffer_ptr += size;
00203 
00204                 if (marker == APP13 && size >= 16) { /* audio data */
00205                     /* time (GMT) of first sample in usec since 1970, little-endian */
00206                     pkt->pts = pkt->dts = AV_RL64(startmarker_ptr + 8);
00207                     pkt->stream_index = AUDIO_STREAM_INDEX;
00208                     pkt->destruct = NULL;
00209                     pkt->size = size - 14;
00210                     pkt->data = startmarker_ptr + 16;
00211 
00212                     if (startmarker_ptr - mxg->buffer > mxg->cache_size) {
00213                         if (mxg->cache_size > 0) {
00214                             memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);
00215                         }
00216                         mxg->buffer_ptr = mxg->buffer;
00217                     }
00218 
00219                     return pkt->size;
00220                 } else if (marker == COM && size >= 18 &&
00221                            !strncmp(startmarker_ptr + 4, "MXF", 3)) {
00222                     /* time (GMT) of video frame in usec since 1970, little-endian */
00223                     mxg->dts = AV_RL64(startmarker_ptr + 12);
00224                 }
00225             }
00226         } else {
00227             /* start marker not found */
00228             mxg->buffer_ptr = search_end;
00229             mxg->cache_size = OVERREAD_SIZE;
00230         }
00231     }
00232 
00233     return AVERROR_EOF;
00234 }
00235 
00236 static int mxg_close(struct AVFormatContext *s)
00237 {
00238     MXGContext *mxg = s->priv_data;
00239     av_freep(&mxg->buffer);
00240     return 0;
00241 }
00242 
00243 AVInputFormat ff_mxg_demuxer = {
00244     .name = "mxg",
00245     .long_name = NULL_IF_CONFIG_SMALL("MxPEG clip file format"),
00246     .priv_data_size = sizeof(MXGContext),
00247     .read_header = mxg_read_header,
00248     .read_packet = mxg_read_packet,
00249     .read_close = mxg_close,
00250     .extensions = "mxg"
00251 };