FFmpeg: libavformat/rtpdec_h263_rfc2190.c Source File

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libavformat

rtpdec_h263_rfc2190.c

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1 /*

2 * RTP H.263 Depacketizer, RFC 2190

4 * Based on the GStreamer H.263 Depayloder:

10 *

11 * This file is part of Libav.

12 *

13 * Libav is free software; you can redistribute it and/or

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

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

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

17 *

18 * Libav is distributed in the hope that it will be useful,

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

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

21 * Lesser General Public License for more details.

22 *

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

24 * License along with Libav; if not, write to the Free Software

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

26 */

28 #include "avformat.h"

29 #include "rtpdec_formats.h"

30 #include "libavutil/attributes.h"

31 #include "libavutil/intreadwrite.h"

32 #include "libavcodec/get_bits.h"

34 struct PayloadContext {

35 AVIOContext *buf;

36 uint8_t endbyte;

37 int endbyte_bits;

38 uint32_t timestamp;

39 int newformat;

40 };

42 static PayloadContext *h263_new_context(void)

43 {

44 return av_mallocz(sizeof(PayloadContext));

45 }

47 static void h263_free_context(PayloadContext *data)

48 {

49 if (!data)

50 return;

51 if (data->buf) {

52 uint8_t *p;

53 avio_close_dyn_buf(data->buf, &p);

54 av_free(p);

55 }

56 av_free(data);

57 }

59 static av_cold int h263_init(AVFormatContext *ctx, int st_index, PayloadContext *data)

60 {

61 if (st_index < 0)

62 return 0;

63 ctx->streams[st_index]->need_parsing = AVSTREAM_PARSE_FULL;

64 return 0;

65 }

67 static int h263_handle_packet(AVFormatContext *ctx, PayloadContext *data,

68 AVStream *st, AVPacket *pkt, uint32_t *timestamp,

69 const uint8_t *buf, int len, uint16_t seq,

70 int flags)

71 {

72 /* Corresponding to header fields in the RFC */

73 int f, p, i, sbit, ebit, src, r;

74 int header_size, ret;

76 if (data->newformat)

77 return ff_h263_handle_packet(ctx, data, st, pkt, timestamp, buf, len,

78 seq, flags);

80 if (data->buf && data->timestamp != *timestamp) {

81 /* Dropping old buffered, unfinished data */

82 uint8_t *p;

83 avio_close_dyn_buf(data->buf, &p);

84 av_free(p);

85 data->buf = NULL;

86 }

88 if (len < 4) {

89 av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet: %d\n", len);

90 return AVERROR_INVALIDDATA;

91 }

93 f = buf[0] & 0x80;

94 p = buf[0] & 0x40;

95 if (!f) {

96 /* Mode A */

97 header_size = 4;

98 i = buf[1] & 0x10;

99 r = ((buf[1] & 0x01) << 3) | ((buf[2] & 0xe0) >> 5);

100 } else if (!p) {

101 /* Mode B */

102 header_size = 8;

103 if (len < header_size) {

104 av_log(ctx, AV_LOG_ERROR,

105 "Too short H.263 RTP packet: %d bytes, %d header bytes\n",

106 len, header_size);

107 return AVERROR_INVALIDDATA;

108 }

109 r = buf[3] & 0x03;

110 i = buf[4] & 0x80;

111 } else {

112 /* Mode C */

113 header_size = 12;

114 if (len < header_size) {

115 av_log(ctx, AV_LOG_ERROR,

116 "Too short H.263 RTP packet: %d bytes, %d header bytes\n",

117 len, header_size);

118 return AVERROR_INVALIDDATA;

119 }

120 r = buf[3] & 0x03;

121 i = buf[4] & 0x80;

122 }

123 sbit = (buf[0] >> 3) & 0x7;

124 ebit = buf[0] & 0x7;

125 src = (buf[1] & 0xe0) >> 5;

126 if (!(buf[0] & 0xf8)) { /* Reserved bits in RFC 2429/4629 are zero */

127 if ((src == 0 || src >= 6) && r) {

128 /* Invalid src for this format, and bits that should be zero

129 * according to RFC 2190 aren't zero. */

130 av_log(ctx, AV_LOG_WARNING,

131 "Interpreting H263 RTP data as RFC 2429/4629 even though "

132 "signalled with a static payload type.\n");

133 data->newformat = 1;

134 return ff_h263_handle_packet(ctx, data, st, pkt, timestamp, buf,

135 len, seq, flags);

136 }

137 }

138

139 buf += header_size;

140 len -= header_size;

141

142 if (!data->buf) {

143 /* Check the picture start code, only start buffering a new frame

144 * if this is correct */

145 if (len > 4 && AV_RB32(buf) >> 10 == 0x20) {

146 ret = avio_open_dyn_buf(&data->buf);

147 if (ret < 0)

148 return ret;

149 data->timestamp = *timestamp;

150 } else {

151 /* Frame not started yet, skipping */

152 return AVERROR(EAGAIN);

153 }

154 }

155

156 if (data->endbyte_bits || sbit) {

157 if (data->endbyte_bits == sbit) {

158 data->endbyte |= buf[0] & (0xff >> sbit);

159 data->endbyte_bits = 0;

160 buf++;

161 len--;

162 avio_w8(data->buf, data->endbyte);

163 } else {

164 /* Start/end skip bits not matching - missed packets? */

165 GetBitContext gb;

166 init_get_bits(&gb, buf, len*8 - ebit);

167 skip_bits(&gb, sbit);

168 if (data->endbyte_bits) {

169 data->endbyte |= get_bits(&gb, 8 - data->endbyte_bits);

170 avio_w8(data->buf, data->endbyte);

171 }

172 while (get_bits_left(&gb) >= 8)

173 avio_w8(data->buf, get_bits(&gb, 8));

174 data->endbyte_bits = get_bits_left(&gb);

175 if (data->endbyte_bits)

176 data->endbyte = get_bits(&gb, data->endbyte_bits) <<

177 (8 - data->endbyte_bits);

178 ebit = 0;

179 len = 0;

180 }

181 }

182 if (ebit) {

183 if (len > 0)

184 avio_write(data->buf, buf, len - 1);

185 data->endbyte_bits = 8 - ebit;

186 data->endbyte = buf[len - 1] & (0xff << ebit);

187 } else {

188 avio_write(data->buf, buf, len);

189 }

190

191 if (!(flags & RTP_FLAG_MARKER))

192 return AVERROR(EAGAIN);

193

194 if (data->endbyte_bits)

195 avio_w8(data->buf, data->endbyte);

196 data->endbyte_bits = 0;

197

198 ret = ff_rtp_finalize_packet(pkt, &data->buf, st->index);

199 if (ret < 0)

200 return ret;

201 if (!i)

202 pkt->flags |= AV_PKT_FLAG_KEY;

203

204 return 0;

205 }

206

207 RTPDynamicProtocolHandler ff_h263_rfc2190_dynamic_handler = {

208 .codec_type = AVMEDIA_TYPE_VIDEO,

209 .codec_id = AV_CODEC_ID_H263,

210 .init = h263_init,

211 .parse_packet = h263_handle_packet,

212 .alloc = h263_new_context,

213 .free = h263_free_context,

214 .static_payload_id = 34,

215 };

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