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/channel_layout.h"
00023 #include "libavutil/intreadwrite.h"
00024 #include "libavcodec/mjpeg.h"
00025 #include "avformat.h"
00026 #include "internal.h"
00027 #include "avio.h"
00028 
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)
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 = avformat_new_stream(s, NULL);
00048     if (!video_st)
00049         return AVERROR(ENOMEM);
00050     video_st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
00051     video_st->codec->codec_id = AV_CODEC_ID_MXPEG;
00052     avpriv_set_pts_info(video_st, 64, 1, 1000000);
00053 
00054     audio_st = avformat_new_stream(s, NULL);
00055     if (!audio_st)
00056         return AVERROR(ENOMEM);
00057     audio_st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
00058     audio_st->codec->codec_id = AV_CODEC_ID_PCM_ALAW;
00059     audio_st->codec->channels = 1;
00060     audio_st->codec->channel_layout = AV_CH_LAYOUT_MONO;
00061     audio_st->codec->sample_rate = 8000;
00062     audio_st->codec->bits_per_coded_sample = 8;
00063     audio_st->codec->block_align = 1;
00064     avpriv_set_pts_info(audio_st, 64, 1, 1000000);
00065 
00066     mxg->soi_ptr = mxg->buffer_ptr = mxg->buffer = 0;
00067     mxg->buffer_size = 0;
00068     mxg->dts = AV_NOPTS_VALUE;
00069     mxg->cache_size = 0;
00070 
00071     return 0;
00072 }
00073 
00074 static uint8_t* mxg_find_startmarker(uint8_t *p, uint8_t *end)
00075 {
00076     for (; p < end - 3; p += 4) {
00077         uint32_t x = *(uint32_t*)p;
00078 
00079         if (x & (~(x+0x01010101)) & 0x80808080) {
00080             if (p[0] == 0xff) {
00081                 return p;
00082             } else if (p[1] == 0xff) {
00083                 return p+1;
00084             } else if (p[2] == 0xff) {
00085                 return p+2;
00086             } else if (p[3] == 0xff) {
00087                 return p+3;
00088             }
00089         }
00090     }
00091 
00092     for (; p < end; ++p) {
00093         if (*p == 0xff) return p;
00094     }
00095 
00096     return end;
00097 }
00098 
00099 static int mxg_update_cache(AVFormatContext *s, unsigned int cache_size)
00100 {
00101     MXGContext *mxg = s->priv_data;
00102     unsigned int current_pos = mxg->buffer_ptr - mxg->buffer;
00103     unsigned int soi_pos;
00104     int ret;
00105 
00106     /* reallocate internal buffer */
00107     if (current_pos > current_pos + cache_size)
00108         return AVERROR(ENOMEM);
00109     soi_pos = mxg->soi_ptr - mxg->buffer;
00110     mxg->buffer = av_fast_realloc(mxg->buffer, &mxg->buffer_size,
00111                                   current_pos + cache_size +
00112                                   FF_INPUT_BUFFER_PADDING_SIZE);
00113     if (!mxg->buffer)
00114         return AVERROR(ENOMEM);
00115     mxg->buffer_ptr = mxg->buffer + current_pos;
00116     if (mxg->soi_ptr) mxg->soi_ptr = mxg->buffer + soi_pos;
00117 
00118     /* get data */
00119     ret = avio_read(s->pb, mxg->buffer_ptr + mxg->cache_size,
00120                      cache_size - mxg->cache_size);
00121     if (ret < 0)
00122         return ret;
00123 
00124     mxg->cache_size += ret;
00125 
00126     return ret;
00127 }
00128 
00129 static int mxg_read_packet(AVFormatContext *s, AVPacket *pkt)
00130 {
00131     int ret;
00132     unsigned int size;
00133     uint8_t *startmarker_ptr, *end, *search_end, marker;
00134     MXGContext *mxg = s->priv_data;
00135 
00136     while (!url_feof(s->pb) && !s->pb->error){
00137         if (mxg->cache_size <= OVERREAD_SIZE) {
00138             /* update internal buffer */
00139             ret = mxg_update_cache(s, DEFAULT_PACKET_SIZE + OVERREAD_SIZE);
00140             if (ret < 0)
00141                 return ret;
00142         }
00143         end = mxg->buffer_ptr + mxg->cache_size;
00144 
00145         /* find start marker - 0xff */
00146         if (mxg->cache_size > OVERREAD_SIZE) {
00147             search_end = end - OVERREAD_SIZE;
00148             startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);
00149         } else {
00150             search_end = end;
00151             startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);
00152             if (startmarker_ptr >= search_end - 1 ||
00153                 *(startmarker_ptr + 1) != EOI) break;
00154         }
00155 
00156         if (startmarker_ptr != search_end) { /* start marker found */
00157             marker = *(startmarker_ptr + 1);
00158             mxg->buffer_ptr = startmarker_ptr + 2;
00159             mxg->cache_size = end - mxg->buffer_ptr;
00160 
00161             if (marker == SOI) {
00162                 mxg->soi_ptr = startmarker_ptr;
00163             } else if (marker == EOI) {
00164                 if (!mxg->soi_ptr) {
00165                     av_log(s, AV_LOG_WARNING, "Found EOI before SOI, skipping\n");
00166                     continue;
00167                 }
00168 
00169                 pkt->pts = pkt->dts = mxg->dts;
00170                 pkt->stream_index = 0;
00171                 pkt->destruct = NULL;
00172                 pkt->size = mxg->buffer_ptr - mxg->soi_ptr;
00173                 pkt->data = mxg->soi_ptr;
00174 
00175                 if (mxg->soi_ptr - mxg->buffer > mxg->cache_size) {
00176                     if (mxg->cache_size > 0) {
00177                         memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);
00178                     }
00179 
00180                     mxg->buffer_ptr = mxg->buffer;
00181                 }
00182                 mxg->soi_ptr = 0;
00183 
00184                 return pkt->size;
00185             } else if ( (SOF0 <= marker && marker <= SOF15) ||
00186                         (SOS  <= marker && marker <= COM) ) {
00187                 /* all other markers that start marker segment also contain
00188                    length value (see specification for JPEG Annex B.1) */
00189                 size = AV_RB16(mxg->buffer_ptr);
00190                 if (size < 2)
00191                     return AVERROR(EINVAL);
00192 
00193                 if (mxg->cache_size < size) {
00194                     ret = mxg_update_cache(s, size);
00195                     if (ret < 0)
00196                         return ret;
00197                     startmarker_ptr = mxg->buffer_ptr - 2;
00198                     mxg->cache_size = 0;
00199                 } else {
00200                     mxg->cache_size -= size;
00201                 }
00202 
00203                 mxg->buffer_ptr += size;
00204 
00205                 if (marker == APP13 && size >= 16) { /* audio data */
00206                     /* time (GMT) of first sample in usec since 1970, little-endian */
00207                     pkt->pts = pkt->dts = AV_RL64(startmarker_ptr + 8);
00208                     pkt->stream_index = 1;
00209                     pkt->destruct = NULL;
00210                     pkt->size = size - 14;
00211                     pkt->data = startmarker_ptr + 16;
00212 
00213                     if (startmarker_ptr - mxg->buffer > mxg->cache_size) {
00214                         if (mxg->cache_size > 0) {
00215                             memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);
00216                         }
00217                         mxg->buffer_ptr = mxg->buffer;
00218                     }
00219 
00220                     return pkt->size;
00221                 } else if (marker == COM && size >= 18 &&
00222                            !strncmp(startmarker_ptr + 4, "MXF", 3)) {
00223                     /* time (GMT) of video frame in usec since 1970, little-endian */
00224                     mxg->dts = AV_RL64(startmarker_ptr + 12);
00225                 }
00226             }
00227         } else {
00228             /* start marker not found */
00229             mxg->buffer_ptr = search_end;
00230             mxg->cache_size = OVERREAD_SIZE;
00231         }
00232     }
00233 
00234     return AVERROR_EOF;
00235 }
00236 
00237 static int mxg_close(struct AVFormatContext *s)
00238 {
00239     MXGContext *mxg = s->priv_data;
00240     av_freep(&mxg->buffer);
00241     return 0;
00242 }
00243 
00244 AVInputFormat ff_mxg_demuxer = {
00245     .name           = "mxg",
00246     .long_name      = NULL_IF_CONFIG_SMALL("MxPEG clip"),
00247     .priv_data_size = sizeof(MXGContext),
00248     .read_header    = mxg_read_header,
00249     .read_packet    = mxg_read_packet,
00250     .read_close     = mxg_close,
00251     .extensions     = "mxg",
00252 };