Benny Prijono | c45d951 | 2010-12-10 11:04:30 +0000 | [diff] [blame] | 1 | /* $Id$ */ |
| 2 | /* |
| 3 | * Copyright (C) 2008-2009 Teluu Inc. (http://www.teluu.com) |
| 4 | * |
| 5 | * This program is free software; you can redistribute it and/or modify |
| 6 | * it under the terms of the GNU General Public License as published by |
| 7 | * the Free Software Foundation; either version 2 of the License, or |
| 8 | * (at your option) any later version. |
| 9 | * |
| 10 | * This program is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | * GNU General Public License for more details. |
| 14 | * |
| 15 | * You should have received a copy of the GNU General Public License |
| 16 | * along with this program; if not, write to the Free Software |
| 17 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 18 | */ |
| 19 | #ifndef __PJMEDIA_H263_PACKETIZER_H__ |
| 20 | #define __PJMEDIA_H263_PACKETIZER_H__ |
| 21 | |
| 22 | |
| 23 | /** |
| 24 | * @file h263_packetizer.h |
| 25 | * @brief Packetizes H.263 bitstream into RTP payload. |
| 26 | */ |
| 27 | |
| 28 | #include <pj/errno.h> |
| 29 | |
| 30 | PJ_BEGIN_DECL |
| 31 | |
| 32 | /** |
| 33 | * Find synchronization point (PSC, slice, GSBC, EOS, EOSBS) in H.263 |
| 34 | * bitstream, in reversed manner. |
| 35 | */ |
| 36 | PJ_INLINE(pj_uint8_t*) pjmedia_h263_find_sync_point_rev(pj_uint8_t *data, |
| 37 | pj_size_t data_len) |
| 38 | { |
| 39 | pj_uint8_t *p = data+data_len-1; |
| 40 | |
| 41 | while (p > data && *p && *(p+1)) |
| 42 | --p; |
| 43 | |
| 44 | if (p == data) |
| 45 | return (data + data_len); |
| 46 | |
| 47 | return p; |
| 48 | } |
| 49 | |
| 50 | /** |
| 51 | * Generate an RTP payload from H.263 frame bitstream, in-place processing. |
| 52 | */ |
| 53 | PJ_INLINE(pj_status_t) pjmedia_h263_packetize(pj_uint8_t *buf, |
| 54 | pj_size_t buf_len, |
| 55 | unsigned *pos, |
| 56 | int max_payload_len, |
| 57 | const pj_uint8_t **payload, |
| 58 | pj_size_t *payload_len) |
| 59 | { |
| 60 | pj_uint8_t *p, *p_end; |
| 61 | |
| 62 | p = buf + *pos; |
| 63 | p_end = buf + buf_len; |
| 64 | |
| 65 | /* Put two octets payload header */ |
| 66 | if ((p_end-p > 2) && *p==0 && *(p+1)==0) { |
| 67 | /* The bitstream starts with synchronization point, just override |
| 68 | * the two zero octets (sync point mark) for payload header. |
| 69 | */ |
| 70 | *p = 0x04; |
| 71 | } else { |
| 72 | /* Not started in synchronization point, we will use two octets |
| 73 | * preceeding the bitstream for payload header! |
| 74 | */ |
| 75 | pj_assert(*pos>=2); |
| 76 | p -= 2; |
| 77 | *p = 0; |
| 78 | } |
| 79 | *(p+1) = 0; |
| 80 | |
| 81 | /* When bitstream truncation needed because of payload length/MTU |
| 82 | * limitation, try to use sync point for the payload boundary. |
| 83 | */ |
| 84 | if (p_end-p > max_payload_len) { |
| 85 | p_end = pjmedia_h263_find_sync_point_rev(p+2, max_payload_len-2); |
| 86 | } |
| 87 | |
| 88 | *payload = p; |
| 89 | *payload_len = p_end-p; |
| 90 | *pos = p_end - buf; |
| 91 | |
| 92 | return PJ_SUCCESS; |
| 93 | } |
| 94 | |
| 95 | /** |
| 96 | * Append RTP payload to a H.263 picture bitstream. |
| 97 | */ |
| 98 | PJ_INLINE(pj_status_t) pjmedia_h263_unpacketize(const pj_uint8_t *payload, |
| 99 | pj_size_t payload_len, |
| 100 | pj_uint8_t *bits, |
| 101 | pj_size_t *bits_len) |
| 102 | { |
| 103 | pj_uint8_t P, V, PLEN; |
| 104 | const pj_uint8_t *p=payload; |
| 105 | pj_size_t max_len = *bits_len; |
| 106 | |
| 107 | P = *p & 0x04; |
| 108 | V = *p & 0x02; |
| 109 | PLEN = ((*p & 0x01) << 5) + ((*(p+1) & 0xF8)>>3); |
| 110 | |
| 111 | /* Get bitstream pointer */ |
| 112 | p += 2; |
| 113 | if (V) |
| 114 | p += 1; /* Skip VRC data */ |
| 115 | if (PLEN) |
| 116 | p += PLEN; /* Skip extra picture header data */ |
| 117 | |
| 118 | /* Get bitstream length */ |
| 119 | payload_len -= (p-payload); |
| 120 | |
| 121 | *bits_len = payload_len + (P?2:0); |
| 122 | PJ_ASSERT_RETURN(max_len >= *bits_len, PJ_ETOOSMALL); |
| 123 | |
| 124 | /* Add two zero octets when payload flagged with sync point */ |
| 125 | if (P) { |
| 126 | *bits++ = 0; |
| 127 | *bits++ = 0; |
| 128 | } |
| 129 | |
| 130 | /* Add the bitstream */ |
| 131 | pj_memcpy(bits, p, payload_len); |
| 132 | |
| 133 | return PJ_SUCCESS; |
| 134 | } |
| 135 | |
| 136 | |
| 137 | PJ_END_DECL |
| 138 | |
| 139 | |
| 140 | #endif /* __PJMEDIA_H263_PACKETIZER_H__ */ |