FFmpeg: libavcodec/libgsmdec.c Source File

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libavcodec

libgsmdec.c

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1 /*

2 * Interface to libgsm for GSM decoding

5 *

6 * This file is part of FFmpeg.

7 *

8 * FFmpeg is free software; you can redistribute it and/or

9 * modify it under the terms of the GNU Lesser General Public

10 * License as published by the Free Software Foundation; either

11 * version 2.1 of the License, or (at your option) any later version.

12 *

13 * FFmpeg is distributed in the hope that it will be useful,

14 * but WITHOUT ANY WARRANTY; without even the implied warranty of

15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

16 * Lesser General Public License for more details.

17 *

18 * You should have received a copy of the GNU Lesser General Public

19 * License along with FFmpeg; if not, write to the Free Software

20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

21 */

23 /**

24 * @file

25 * Interface to libgsm for GSM decoding

26 */

28 // The idiosyncrasies of GSM-in-WAV are explained at http://kbs.cs.tu-berlin.de/~jutta/toast.html

30 #include "config.h"

31 #if HAVE_GSM_H

32 #include <gsm.h>

33 #else

34 #include <gsm/gsm.h>

35 #endif

37 #include "libavutil/channel_layout.h"

38 #include "libavutil/common.h"

40 #include "avcodec.h"

41 #include "internal.h"

42 #include "gsm.h"

44 typedef struct LibGSMDecodeContext {

45 struct gsm_state *state;

46 } LibGSMDecodeContext;

48 static av_cold int libgsm_decode_init(AVCodecContext *avctx) {

49 LibGSMDecodeContext *s = avctx->priv_data;

51 avctx->channels = 1;

52 avctx->channel_layout = AV_CH_LAYOUT_MONO;

53 if (!avctx->sample_rate)

54 avctx->sample_rate = 8000;

55 avctx->sample_fmt = AV_SAMPLE_FMT_S16;

57 s->state = gsm_create();

59 switch(avctx->codec_id) {

60 case AV_CODEC_ID_GSM:

61 avctx->frame_size = GSM_FRAME_SIZE;

62 avctx->block_align = GSM_BLOCK_SIZE;

63 break;

64 case AV_CODEC_ID_GSM_MS: {

65 int one = 1;

66 gsm_option(s->state, GSM_OPT_WAV49, &one);

67 avctx->frame_size = 2 * GSM_FRAME_SIZE;

68 avctx->block_align = GSM_MS_BLOCK_SIZE;

69 }

70 }

72 return 0;

73 }

75 static av_cold int libgsm_decode_close(AVCodecContext *avctx) {

76 LibGSMDecodeContext *s = avctx->priv_data;

78 gsm_destroy(s->state);

79 s->state = NULL;

80 return 0;

81 }

83 static int libgsm_decode_frame(AVCodecContext *avctx, void *data,

84 int *got_frame_ptr, AVPacket *avpkt)

85 {

86 int i, ret;

87 LibGSMDecodeContext *s = avctx->priv_data;

88 AVFrame *frame = data;

89 uint8_t *buf = avpkt->data;

90 int buf_size = avpkt->size;

91 int16_t *samples;

93 if (buf_size < avctx->block_align) {

94 av_log(avctx, AV_LOG_ERROR, "Packet is too small\n");

95 return AVERROR_INVALIDDATA;

96 }

98 /* get output buffer */

99 frame->nb_samples = avctx->frame_size;

100 if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)

101 return ret;

102 samples = (int16_t *)frame->data[0];

103

104 for (i = 0; i < avctx->frame_size / GSM_FRAME_SIZE; i++) {

105 if ((ret = gsm_decode(s->state, buf, samples)) < 0)

106 return -1;

107 buf += GSM_BLOCK_SIZE;

108 samples += GSM_FRAME_SIZE;

109 }

110

111 *got_frame_ptr = 1;

112

113 return avctx->block_align;

114 }

115

116 static void libgsm_flush(AVCodecContext *avctx) {

117 LibGSMDecodeContext *s = avctx->priv_data;

118 int one = 1;

119

120 gsm_destroy(s->state);

121 s->state = gsm_create();

122 if (avctx->codec_id == AV_CODEC_ID_GSM_MS)

123 gsm_option(s->state, GSM_OPT_WAV49, &one);

124 }

125

126 #if CONFIG_LIBGSM_DECODER

127 AVCodec ff_libgsm_decoder = {

128 .name = "libgsm",

129 .long_name = NULL_IF_CONFIG_SMALL("libgsm GSM"),

130 .type = AVMEDIA_TYPE_AUDIO,

131 .id = AV_CODEC_ID_GSM,

132 .priv_data_size = sizeof(LibGSMDecodeContext),

133 .init = libgsm_decode_init,

134 .close = libgsm_decode_close,

135 .decode = libgsm_decode_frame,

136 .flush = libgsm_flush,

137 .capabilities = CODEC_CAP_DR1,

138 };

139 #endif

140 #if CONFIG_LIBGSM_MS_DECODER

141 AVCodec ff_libgsm_ms_decoder = {

142 .name = "libgsm_ms",

143 .long_name = NULL_IF_CONFIG_SMALL("libgsm GSM Microsoft variant"),

144 .type = AVMEDIA_TYPE_AUDIO,

145 .id = AV_CODEC_ID_GSM_MS,

146 .priv_data_size = sizeof(LibGSMDecodeContext),

147 .init = libgsm_decode_init,

148 .close = libgsm_decode_close,

149 .decode = libgsm_decode_frame,

150 .flush = libgsm_flush,

151 .capabilities = CODEC_CAP_DR1,

152 };

153 #endif

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