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libavformat/yop.c

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00001 
00026 #include "libavutil/intreadwrite.h"
00027 #include "avformat.h"
00028 
00029 typedef struct yop_dec_context {
00030     AVPacket video_packet;
00031 
00032     int odd_frame;
00033     int frame_size;
00034     int audio_block_length;
00035     int palette_size;
00036 } YopDecContext;
00037 
00038 static int yop_probe(AVProbeData *probe_packet)
00039 {
00040     if (AV_RB16(probe_packet->buf) == AV_RB16("YO")  &&
00041         probe_packet->buf[6]                         &&
00042         probe_packet->buf[7]                         &&
00043         !(probe_packet->buf[8] & 1)                  &&
00044         !(probe_packet->buf[10] & 1))
00045         return AVPROBE_SCORE_MAX * 3 / 4;
00046 
00047     return 0;
00048 }
00049 
00050 static int yop_read_header(AVFormatContext *s, AVFormatParameters *ap)
00051 {
00052     YopDecContext *yop = s->priv_data;
00053     ByteIOContext *pb  = s->pb;
00054 
00055     AVCodecContext *audio_dec, *video_dec;
00056     AVStream *audio_stream, *video_stream;
00057 
00058     int frame_rate, ret;
00059 
00060     audio_stream = av_new_stream(s, 0);
00061     video_stream = av_new_stream(s, 1);
00062 
00063     // Extra data that will be passed to the decoder
00064     video_stream->codec->extradata_size = 8;
00065 
00066     video_stream->codec->extradata = av_mallocz(video_stream->codec->extradata_size +
00067                                                 FF_INPUT_BUFFER_PADDING_SIZE);
00068 
00069     if (!video_stream->codec->extradata)
00070         return AVERROR(ENOMEM);
00071 
00072     // Audio
00073     audio_dec               = audio_stream->codec;
00074     audio_dec->codec_type   = AVMEDIA_TYPE_AUDIO;
00075     audio_dec->codec_id     = CODEC_ID_ADPCM_IMA_WS;
00076     audio_dec->channels     = 1;
00077     audio_dec->sample_rate  = 22050;
00078 
00079     // Video
00080     video_dec               = video_stream->codec;
00081     video_dec->codec_type   = AVMEDIA_TYPE_VIDEO;
00082     video_dec->codec_id     = CODEC_ID_YOP;
00083 
00084     url_fskip(pb, 6);
00085 
00086     frame_rate              = get_byte(pb);
00087     yop->frame_size         = get_byte(pb) * 2048;
00088     video_dec->width        = get_le16(pb);
00089     video_dec->height       = get_le16(pb);
00090 
00091     video_stream->sample_aspect_ratio = (AVRational){1, 2};
00092 
00093     ret = get_buffer(pb, video_dec->extradata, 8);
00094     if (ret < 8)
00095         return ret < 0 ? ret : AVERROR_EOF;
00096 
00097     yop->palette_size       = video_dec->extradata[0] * 3 + 4;
00098     yop->audio_block_length = AV_RL16(video_dec->extradata + 6);
00099 
00100     // 1840 samples per frame, 1 nibble per sample; hence 1840/2 = 920
00101     if (yop->audio_block_length < 920 ||
00102         yop->audio_block_length + yop->palette_size >= yop->frame_size) {
00103         av_log(s, AV_LOG_ERROR, "YOP has invalid header\n");
00104         return AVERROR_INVALIDDATA;
00105     }
00106 
00107     url_fseek(pb, 2048, SEEK_SET);
00108 
00109     av_set_pts_info(video_stream, 32, 1, frame_rate);
00110 
00111     return 0;
00112 }
00113 
00114 static int yop_read_packet(AVFormatContext *s, AVPacket *pkt)
00115 {
00116     YopDecContext *yop = s->priv_data;
00117     ByteIOContext *pb  = s->pb;
00118 
00119     int ret;
00120     int actual_video_data_size = yop->frame_size -
00121                                  yop->audio_block_length - yop->palette_size;
00122 
00123     yop->video_packet.stream_index = 1;
00124 
00125     if (yop->video_packet.data) {
00126         *pkt                   =  yop->video_packet;
00127         yop->video_packet.data =  NULL;
00128         yop->video_packet.size =  0;
00129         pkt->data[0]           =  yop->odd_frame;
00130         pkt->flags             |= AV_PKT_FLAG_KEY;
00131         yop->odd_frame         ^= 1;
00132         return pkt->size;
00133     }
00134     ret = av_new_packet(&yop->video_packet,
00135                         yop->frame_size - yop->audio_block_length);
00136     if (ret < 0)
00137         return ret;
00138 
00139     yop->video_packet.pos = url_ftell(pb);
00140 
00141     ret = get_buffer(pb, yop->video_packet.data, yop->palette_size);
00142     if (ret < 0) {
00143         goto err_out;
00144     }else if (ret < yop->palette_size) {
00145         ret = AVERROR_EOF;
00146         goto err_out;
00147     }
00148 
00149     ret = av_get_packet(pb, pkt, 920);
00150     if (ret < 0)
00151         goto err_out;
00152 
00153     // Set position to the start of the frame
00154     pkt->pos = yop->video_packet.pos;
00155 
00156     url_fskip(pb, yop->audio_block_length - ret);
00157 
00158     ret = get_buffer(pb, yop->video_packet.data + yop->palette_size,
00159                      actual_video_data_size);
00160     if (ret < 0)
00161         goto err_out;
00162     else if (ret < actual_video_data_size)
00163         av_shrink_packet(&yop->video_packet, yop->palette_size + ret);
00164 
00165     // Arbitrarily return the audio data first
00166     return yop->audio_block_length;
00167 
00168 err_out:
00169     av_free_packet(&yop->video_packet);
00170     return ret;
00171 }
00172 
00173 static int yop_read_close(AVFormatContext *s)
00174 {
00175     YopDecContext *yop = s->priv_data;
00176     av_free_packet(&yop->video_packet);
00177     return 0;
00178 }
00179 
00180 static int yop_read_seek(AVFormatContext *s, int stream_index,
00181                          int64_t timestamp, int flags)
00182 {
00183     YopDecContext *yop = s->priv_data;
00184     int64_t frame_pos, pos_min, pos_max;
00185     int frame_count;
00186 
00187     av_free_packet(&yop->video_packet);
00188 
00189     if (!stream_index)
00190         return -1;
00191 
00192     pos_min        = s->data_offset;
00193     pos_max        = url_fsize(s->pb) - yop->frame_size;
00194     frame_count    = (pos_max - pos_min) / yop->frame_size;
00195 
00196     timestamp      = FFMAX(0, FFMIN(frame_count, timestamp));
00197 
00198     frame_pos      = timestamp * yop->frame_size + pos_min;
00199     yop->odd_frame = timestamp & 1;
00200 
00201     url_fseek(s->pb, frame_pos, SEEK_SET);
00202     return 0;
00203 }
00204 
00205 AVInputFormat yop_demuxer = {
00206     "yop",
00207     NULL_IF_CONFIG_SMALL("Psygnosis YOP Format"),
00208     sizeof(YopDecContext),
00209     yop_probe,
00210     yop_read_header,
00211     yop_read_packet,
00212     yop_read_close,
00213     yop_read_seek,
00214     .extensions = "yop",
00215     .flags = AVFMT_GENERIC_INDEX,
00216 };

Generated on Fri Sep 16 2011 17:17:47 for FFmpeg by  doxygen 1.7.1