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#include "libavutil/channel_layout.h" |
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#include "libavutil/mathematics.h" |
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#include "libavutil/opt.h" |
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#include "avformat.h" |
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#include "internal.h" |
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#define GSM_BLOCK_SIZE 33 |
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#define GSM_BLOCK_SAMPLES 160 |
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#define GSM_SAMPLE_RATE 8000 |
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typedef struct GSMDemuxerContext { |
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AVClass *class; |
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int sample_rate; |
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} GSMDemuxerContext; |
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static int gsm_probe(const AVProbeData *p) |
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{ |
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int valid = 0, invalid = 0; |
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uint8_t *b = p->buf; |
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while (b < p->buf + p->buf_size - 32) { |
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if ((*b & 0xf0) == 0xd0) { |
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valid++; |
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} else { |
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invalid++; |
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} |
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b += 33; |
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} |
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if (valid >> 5 > invalid) |
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return AVPROBE_SCORE_EXTENSION + 1; |
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return 0; |
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} |
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static int gsm_read_packet(AVFormatContext *s, AVPacket *pkt) |
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{ |
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int ret, size; |
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size = GSM_BLOCK_SIZE; |
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pkt->pos = avio_tell(s->pb); |
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pkt->stream_index = 0; |
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ret = av_get_packet(s->pb, pkt, size); |
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if (ret < GSM_BLOCK_SIZE) { |
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return ret < 0 ? ret : AVERROR(EIO); |
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} |
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pkt->duration = 1; |
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pkt->pts = pkt->pos / GSM_BLOCK_SIZE; |
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return 0; |
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} |
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static int gsm_read_header(AVFormatContext *s) |
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{ |
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GSMDemuxerContext *c = s->priv_data; |
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AVStream *st = avformat_new_stream(s, NULL); |
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if (!st) |
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return AVERROR(ENOMEM); |
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st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO; |
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st->codecpar->codec_id = s->iformat->raw_codec_id; |
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st->codecpar->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO; |
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st->codecpar->sample_rate = c->sample_rate; |
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st->codecpar->bit_rate = GSM_BLOCK_SIZE * 8 * c->sample_rate / GSM_BLOCK_SAMPLES; |
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avpriv_set_pts_info(st, 64, GSM_BLOCK_SAMPLES, GSM_SAMPLE_RATE); |
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return 0; |
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} |
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static const AVOption options[] = { |
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{ "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate), |
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AV_OPT_TYPE_INT, {.i64 = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE, |
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AV_OPT_FLAG_DECODING_PARAM }, |
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{ NULL }, |
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}; |
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static const AVClass gsm_class = { |
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.class_name = "gsm demuxer", |
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.item_name = av_default_item_name, |
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.option = options, |
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.version = LIBAVUTIL_VERSION_INT, |
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}; |
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const AVInputFormat ff_gsm_demuxer = { |
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.name = "gsm", |
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.long_name = NULL_IF_CONFIG_SMALL("raw GSM"), |
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.priv_data_size = sizeof(GSMDemuxerContext), |
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.read_probe = gsm_probe, |
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.read_header = gsm_read_header, |
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.read_packet = gsm_read_packet, |
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.flags = AVFMT_GENERIC_INDEX, |
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.extensions = "gsm", |
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.raw_codec_id = AV_CODEC_ID_GSM, |
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.priv_class = &gsm_class, |
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}; |
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