X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=modules%2Faccess%2Fudp.c;h=f56ee60347fd17e1bdb0edde49eccb02954be05a;hb=a80a435327bb5eda9ae25459ac77c0c1b658cca0;hp=4610ac6abb539bd443c92fd79d77f2d6b02eb6f1;hpb=2799d36bc8abdc28df29a202acdb27223b25a7a7;p=vlc diff --git a/modules/access/udp.c b/modules/access/udp.c index 4610ac6abb..f56ee60347 100644 --- a/modules/access/udp.c +++ b/modules/access/udp.c @@ -1,16 +1,21 @@ /***************************************************************************** - * udp.c: raw UDP access plug-in + * udp.c: raw UDP & RTP input module ***************************************************************************** - * Copyright (C) 2001, 2002 VideoLAN - * $Id: udp.c,v 1.3 2002/09/30 11:05:34 sam Exp $ + * Copyright (C) 2001-2005 the VideoLAN team + * $Id$ * * Authors: Christophe Massiot + * Tristan Leteurtre + * Laurent Aimar + * Jean-Paul Saman + * + * Reviewed: 23 October 2003, Jean-Paul Saman * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. - * + * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the @@ -25,230 +30,583 @@ * Preamble *****************************************************************************/ #include -#include -#include -#include -#include -#include #include #include -#ifdef HAVE_UNISTD_H -# include -#elif defined( _MSC_VER ) && defined( _WIN32 ) -# include -#endif - #include "network.h" -/***************************************************************************** - * Local prototypes - *****************************************************************************/ -static int Open ( vlc_object_t * ); - /***************************************************************************** * Module descriptor *****************************************************************************/ +#define CACHING_TEXT N_("Caching value in ms") +#define CACHING_LONGTEXT N_( \ + "Allows you to modify the default caching value for UDP streams. This " \ + "value should be set in millisecond units." ) + +#define AUTO_MTU_TEXT N_("Autodetection of MTU") +#define AUTO_MTU_LONGTEXT N_( \ + "Allows growing the MTU if truncated packets are found" ) + +#define RTP_LATE_TEXT N_("RTP reordering timeout in ms") +#define RTP_LATE_LONGTEXT N_( \ + "Allows you to modify the RTP reordering behaviour. " \ + "RTP input will wait for late packets upto " \ + "the specified timeout in milisecond units." ) + +static int Open ( vlc_object_t * ); +static void Close( vlc_object_t * ); + vlc_module_begin(); - set_description( _("raw UDP access module") ); - set_capability( "access", 0 ); + set_shortname( _("UDP/RTP" ) ); + set_description( _("UDP/RTP input") ); + set_category( CAT_INPUT ); + set_subcategory( SUBCAT_INPUT_ACCESS ); + + add_integer( "udp-caching", DEFAULT_PTS_DELAY / 1000, NULL, CACHING_TEXT, + CACHING_LONGTEXT, VLC_TRUE ); + add_integer( "rtp-late", 100, NULL, RTP_LATE_TEXT, RTP_LATE_LONGTEXT, VLC_TRUE ); + + add_bool( "udp-auto-mtu", 1, NULL, + AUTO_MTU_TEXT, AUTO_MTU_LONGTEXT, VLC_TRUE ); + + set_capability( "access2", 0 ); add_shortcut( "udp" ); add_shortcut( "udpstream" ); add_shortcut( "udp4" ); add_shortcut( "udp6" ); - set_callbacks( Open, __input_FDNetworkClose ); + add_shortcut( "rtp" ); + add_shortcut( "rtp4" ); + add_shortcut( "rtp6" ); + set_callbacks( Open, Close ); vlc_module_end(); +/***************************************************************************** + * Local prototypes + *****************************************************************************/ +#define RTP_HEADER_LEN 12 + +static block_t *BlockUDP( access_t * ); +static block_t *BlockRTP( access_t * ); +static block_t *BlockChoose( access_t * ); +static int Control( access_t *, int, va_list ); + +struct access_sys_t +{ + int fd; + + int i_mtu; + vlc_bool_t b_auto_mtu; + + /* reorder rtp packets when out-of-sequence */ + int64_t i_rtp_late; + uint16_t i_last_seqno; + block_t *p_list; + block_t *p_end; +}; + /***************************************************************************** * Open: open the socket *****************************************************************************/ static int Open( vlc_object_t *p_this ) { - input_thread_t * p_input = (input_thread_t *)p_this; - input_socket_t * p_access_data; - module_t * p_network; - char * psz_network = ""; - char * psz_name = strdup(p_input->psz_name); - char * psz_parser = psz_name; - char * psz_server_addr = ""; - char * psz_server_port = ""; - char * psz_bind_addr = ""; - char * psz_bind_port = ""; - int i_bind_port = 0, i_server_port = 0; - network_socket_t socket_desc; + access_t *p_access = (access_t*)p_this; + access_sys_t *p_sys; - if( config_GetInt( p_input, "ipv4" ) ) - { - psz_network = "ipv4"; - } - if( config_GetInt( p_input, "ipv6" ) ) - { - psz_network = "ipv6"; - } + char *psz_name = strdup( p_access->psz_path ); + char *psz_parser, *psz_server_addr, *psz_bind_addr = ""; + int i_bind_port, i_server_port = 0; + + /* First set ipv4/ipv6 */ + var_Create( p_access, "ipv4", VLC_VAR_BOOL | VLC_VAR_DOINHERIT ); + var_Create( p_access, "ipv6", VLC_VAR_BOOL | VLC_VAR_DOINHERIT ); - if( *p_input->psz_access ) + if( *p_access->psz_access ) { + vlc_value_t val; /* Find out which shortcut was used */ - if( !strncmp( p_input->psz_access, "udp6", 5 ) ) + if( !strncmp( p_access->psz_access, "udp4", 6 ) || + !strncmp( p_access->psz_access, "rtp4", 6 )) { - psz_network = "ipv6"; + val.b_bool = VLC_TRUE; + var_Set( p_access, "ipv4", val ); + + val.b_bool = VLC_FALSE; + var_Set( p_access, "ipv6", val ); } - else if( !strncmp( p_input->psz_access, "udp4", 5 ) ) + else if( !strncmp( p_access->psz_access, "udp6", 6 ) || + !strncmp( p_access->psz_access, "rtp6", 6 ) ) { - psz_network = "ipv4"; + val.b_bool = VLC_TRUE; + var_Set( p_access, "ipv6", val ); + + val.b_bool = VLC_FALSE; + var_Set( p_access, "ipv4", val ); } } + i_bind_port = var_CreateGetInteger( p_access, "server-port" ); + /* Parse psz_name syntax : * [serveraddr[:serverport]][@[bindaddr]:[bindport]] */ - - if( *psz_parser && *psz_parser != '@' ) + psz_parser = strchr( psz_name, '@' ); + if( psz_parser != NULL ) { - /* Found server */ - psz_server_addr = psz_parser; + /* Found bind address and/or bind port */ + *psz_parser++ = '\0'; + psz_bind_addr = psz_parser; + + if( *psz_parser == '[' ) + /* skips bracket'd IPv6 address */ + psz_parser = strchr( psz_parser, ']' ); - while( *psz_parser && *psz_parser != ':' && *psz_parser != '@' ) + if( psz_parser != NULL ) { - if( *psz_parser == '[' ) + psz_parser = strchr( psz_parser, ':' ); + if( psz_parser != NULL ) { - /* IPv6 address */ - while( *psz_parser && *psz_parser != ']' ) - { - psz_parser++; - } + *psz_parser++ = '\0'; + i_bind_port = atoi( psz_parser ); } - psz_parser++; } + } - if( *psz_parser == ':' ) - { - /* Found server port */ - *psz_parser = '\0'; /* Terminate server name */ - psz_parser++; - psz_server_port = psz_parser; + psz_server_addr = psz_name; + if( *psz_server_addr == '[' ) + /* skips bracket'd IPv6 address */ + psz_parser = strchr( psz_name, ']' ); - while( *psz_parser && *psz_parser != '@' ) - { - psz_parser++; - } + if( psz_parser != NULL ) + { + psz_parser = strchr( psz_parser, ':' ); + if( psz_parser != NULL ) + { + *psz_parser++ = '\0'; + i_server_port = atoi( psz_parser ); } } - if( *psz_parser == '@' ) + msg_Dbg( p_access, "opening server=%s:%d local=%s:%d", + psz_server_addr, i_server_port, psz_bind_addr, i_bind_port ); + + /* Set up p_access */ + p_access->pf_read = NULL; + if( !strcasecmp( p_access->psz_access, "rtp" ) + || !strcasecmp( p_access->psz_access, "rtp4" ) + || !strcasecmp( p_access->psz_access, "rtp6" ) ) + { + p_access->pf_block = BlockRTP; + } + else + { + p_access->pf_block = BlockChoose; + } + p_access->pf_control = Control; + p_access->pf_seek = NULL; + p_access->info.i_update = 0; + p_access->info.i_size = 0; + p_access->info.i_pos = 0; + p_access->info.b_eof = VLC_FALSE; + p_access->info.b_prebuffered = VLC_FALSE; + p_access->info.i_title = 0; + p_access->info.i_seekpoint = 0; + + p_access->p_sys = p_sys = malloc( sizeof( access_sys_t ) ); + p_sys->fd = net_OpenUDP( p_access, psz_bind_addr, i_bind_port, + psz_server_addr, i_server_port ); + if( p_sys->fd < 0 ) { - /* Found bind address or bind port */ - *psz_parser = '\0'; /* Terminate server port or name if necessary */ - psz_parser++; + msg_Err( p_access, "cannot open socket" ); + free( psz_name ); + free( p_sys ); + return VLC_EGENERIC; + } + free( psz_name ); - if( *psz_parser && *psz_parser != ':' ) - { - /* Found bind address */ - psz_bind_addr = psz_parser; + net_StopSend( p_sys->fd ); + + /* FIXME */ + p_sys->i_mtu = var_CreateGetInteger( p_access, "mtu" ); + if( p_sys->i_mtu <= 1 ) + p_sys->i_mtu = 1500; /* Avoid problem */ + + p_sys->b_auto_mtu = var_CreateGetBool( p_access, "udp-auto-mtu" );; + + /* Update default_pts to a suitable value for udp access */ + var_Create( p_access, "udp-caching", VLC_VAR_INTEGER | VLC_VAR_DOINHERIT ); + + + /* RTP reordering for out-of-sequence packets */ + p_sys->i_rtp_late = var_CreateGetInteger( p_access, "rtp-late" ) * 1000; + p_sys->i_last_seqno = 0; + p_sys->p_list = NULL; + p_sys->p_end = NULL; + return VLC_SUCCESS; +} + +/***************************************************************************** + * Close: free unused data structures + *****************************************************************************/ +static void Close( vlc_object_t *p_this ) +{ + access_t *p_access = (access_t*)p_this; + access_sys_t *p_sys = p_access->p_sys; + + block_ChainRelease( p_sys->p_list ); + net_Close( p_sys->fd ); + free( p_sys ); +} + +/***************************************************************************** + * Control: + *****************************************************************************/ +static int Control( access_t *p_access, int i_query, va_list args ) +{ + access_sys_t *p_sys = p_access->p_sys; + vlc_bool_t *pb_bool; + int *pi_int; + int64_t *pi_64; + + switch( i_query ) + { + /* */ + case ACCESS_CAN_SEEK: + case ACCESS_CAN_FASTSEEK: + case ACCESS_CAN_PAUSE: + case ACCESS_CAN_CONTROL_PACE: + pb_bool = (vlc_bool_t*)va_arg( args, vlc_bool_t* ); + *pb_bool = VLC_FALSE; + break; + /* */ + case ACCESS_GET_MTU: + pi_int = (int*)va_arg( args, int * ); + *pi_int = p_sys->i_mtu; + break; + + case ACCESS_GET_PTS_DELAY: + pi_64 = (int64_t*)va_arg( args, int64_t * ); + *pi_64 = var_GetInteger( p_access, "udp-caching" ) * 1000; + break; + + /* */ + case ACCESS_SET_PAUSE_STATE: + case ACCESS_GET_TITLE_INFO: + case ACCESS_SET_TITLE: + case ACCESS_SET_SEEKPOINT: + case ACCESS_SET_PRIVATE_ID_STATE: + return VLC_EGENERIC; + + default: + msg_Warn( p_access, "unimplemented query in control" ); + return VLC_EGENERIC; + + } + return VLC_SUCCESS; +} + +/***************************************************************************** + * BlockUDP: + *****************************************************************************/ +static block_t *BlockUDP( access_t *p_access ) +{ + access_sys_t *p_sys = p_access->p_sys; + block_t *p_block; + + /* Read data */ + p_block = block_New( p_access, p_sys->i_mtu ); + p_block->i_buffer = net_Read( p_access, p_sys->fd, NULL, + p_block->p_buffer, p_sys->i_mtu, + VLC_FALSE ); + if( p_block->i_buffer <= 0 ) + { + block_Release( p_block ); + return NULL; + } + + if( (p_block->i_buffer >= p_sys->i_mtu) && p_sys->b_auto_mtu && + p_sys->i_mtu < 32767 ) + { + /* Increase by 100% */ + p_sys->i_mtu *= 2; + msg_Dbg( p_access, "increasing MTU to %d", p_sys->i_mtu ); + } + + return p_block; +} + +/* + * rtp_ChainInsert - insert a p_block in the chain and + * look at the sequence numbers. + */ +static inline vlc_bool_t rtp_ChainInsert( access_t *p_access, block_t *p_block ) +{ + access_sys_t *p_sys = (access_sys_t *) p_access->p_sys; + block_t *p_prev = NULL; + block_t *p = p_sys->p_end; + uint16_t i_new = (uint16_t) p_block->i_dts; + uint16_t i_tmp = 0; + + if( !p_sys->p_list ) + { + p_sys->p_list = p_block; + p_sys->p_end = p_block; + return VLC_TRUE; + } + /* walk through the queue from top down since the new packet is in + most cases just appended to the end */ - while( *psz_parser && *psz_parser != ':' ) + for( ;; ) + { + i_tmp = i_new - (uint16_t) p->i_dts; + + if( !i_tmp ) /* trash duplicate */ + break; + + if ( i_tmp < 32768 ) + { /* insert after this block ( i_new > p->i_dts ) */ + p_block->p_next = p->p_next; + p->p_next = p_block; + p_block->p_prev = p; + if (p_prev) + { + p_prev->p_prev = p_block; + msg_Dbg(p_access, "RTP reordering: insert after %d, new %d", + (uint16_t) p->i_dts, i_new ); + } + else { - if( *psz_parser == '[' ) - { - /* IPv6 address */ - while( *psz_parser && *psz_parser != ']' ) - { - psz_parser++; - } - } - psz_parser++; + p_sys->p_end = p_block; } + return VLC_TRUE; } + if( p == p_sys->p_list ) + { /* we've reached bottom of chain */ + i_tmp = p_sys->i_last_seqno - i_new; + if( !p_access->info.b_prebuffered || (i_tmp > 32767) ) + { + msg_Dbg(p_access, "RTP reordering: prepend %d before %d", + i_new, (uint16_t) p->i_dts ); + p_block->p_next = p; + p->p_prev = p_block; + p_sys->p_list = p_block; + return VLC_TRUE; + } - if( *psz_parser == ':' ) - { - /* Found bind port */ - *psz_parser = '\0'; /* Terminate bind address if necessary */ - psz_parser++; + if( !i_tmp ) /* trash duplicate */ + break; - psz_bind_port = psz_parser; + /* reordering failed - append the packet to the end of queue */ + msg_Dbg(p_access, "RTP: sequence changed (or buffer too small) " + "new: %d, buffer %d...%d", i_new, (uint16_t) p->i_dts, + (uint16_t) p_sys->p_end->i_dts); + p_sys->p_end->p_next = p_block; + p_block->p_prev = p_sys->p_end; + p_sys->p_end = p_block; + return VLC_TRUE; } + p_prev = p; + p = p->p_prev; } + block_Release( p_block ); + return VLC_FALSE; +} + +/***************************************************************************** + * BlockParseRTP/BlockRTP: + *****************************************************************************/ +static block_t *BlockParseRTP( access_t *p_access, block_t *p_block ) +{ + int i_rtp_version; + int i_CSRC_count; + int i_payload_type; + int i_skip = 0; + int i_extension_flag = 0; + int i_extension_length = 0; + uint16_t i_sequence_number = 0; + + if( p_block == NULL ) + return NULL; + + if( p_block->i_buffer < RTP_HEADER_LEN ) + goto trash; + + /* Parse the header and make some verifications. + * See RFC 3550. */ + i_rtp_version = ( p_block->p_buffer[0] & 0xC0 ) >> 6; + i_CSRC_count = p_block->p_buffer[0] & 0x0F; + i_extension_flag = p_block->p_buffer[0] & 0x10; + i_payload_type = p_block->p_buffer[1] & 0x7F; + i_sequence_number = (p_block->p_buffer[2] << 8 ) + p_block->p_buffer[3]; + + if( i_rtp_version != 2 ) + msg_Dbg( p_access, "RTP version is %u, should be 2", i_rtp_version ); + + if( i_payload_type == 14 || i_payload_type == 32) + i_skip = 4; + else if( i_payload_type != 33 ) + msg_Dbg( p_access, "unsupported RTP payload type (%u)", i_payload_type ); + if( i_extension_flag ) + i_extension_length = 4 + + 4 * ( (p_block->p_buffer[14] << 8) + p_block->p_buffer[15] ); - /* Convert ports format */ - if( *psz_server_port ) + /* Skip header + CSRC extension field n*(32 bits) + extension */ + i_skip += RTP_HEADER_LEN + 4*i_CSRC_count + i_extension_length; + + if( i_skip >= p_block->i_buffer ) + goto trash; + + /* Return the packet without the RTP header, remember seqno in i_dts */ + p_block->i_buffer -= i_skip; + p_block->p_buffer += i_skip; + p_block->i_dts = (mtime_t) i_sequence_number; + +#if 0 + /* Emulate packet loss */ + if ( (i_sequence_number % 4000) == 0) { - i_server_port = strtol( psz_server_port, &psz_parser, 10 ); - if( *psz_parser ) - { - msg_Err( p_input, "cannot parse server port near %s", psz_parser ); - free(psz_name); - return( -1 ); - } + msg_Warn( p_access, "Emulating packet drop" ); + block_Release( p_block ); + return NULL; } +#endif + + return p_block; + + +trash: + msg_Warn( p_access, "received a too short packet for RTP" ); + block_Release( p_block ); + return NULL; +} + +static block_t *BlockPrebufferRTP( access_t *p_access, block_t *p_block ) +{ + access_sys_t *p_sys = p_access->p_sys; + int64_t i_first = mdate(); + int i_count = 0; + block_t *p = p_block; - if( *psz_bind_port ) + for( ;; ) { - i_bind_port = strtol( psz_bind_port, &psz_parser, 10 ); - if( *psz_parser ) + int64_t i_date = mdate(); + + if( p && rtp_ChainInsert( p_access, p )) + i_count++; + + /* Require at least 3 packets in the buffer */ + if( i_count > 3 && (i_date - i_first) > p_sys->i_rtp_late ) + break; + + p = BlockParseRTP( p_access, BlockUDP( p_access )); + if( !p && (i_date - i_first) > p_sys->i_rtp_late ) { - msg_Err( p_input, "cannot parse bind port near %s", psz_parser ); - free(psz_name); - return( -1 ); + msg_Err( p_access, "Error in RTP prebuffering!" ); + break; } } - p_input->pf_read = input_FDNetworkRead; - p_input->pf_set_program = input_SetProgram; - p_input->pf_set_area = NULL; - p_input->pf_seek = NULL; + msg_Dbg( p_access, "RTP: prebuffered %d packets", i_count - 1 ); + p_access->info.b_prebuffered = VLC_TRUE; + p = p_sys->p_list; + p_sys->p_list = p_sys->p_list->p_next; + p_sys->i_last_seqno = (uint16_t) p->i_dts; + p->p_next = NULL; + return p; +} + +static block_t *BlockRTP( access_t *p_access ) +{ + access_sys_t *p_sys = p_access->p_sys; + block_t *p; + +again: + p = BlockParseRTP( p_access, BlockUDP( p_access )); + + if ( !p ) + return NULL; + + if ( !p_access->info.b_prebuffered ) + return BlockPrebufferRTP( p_access, p ); - vlc_mutex_lock( &p_input->stream.stream_lock ); - p_input->stream.b_pace_control = 0; - p_input->stream.b_seekable = 0; - p_input->stream.p_selected_area->i_tell = 0; - p_input->stream.i_method = INPUT_METHOD_NETWORK; - vlc_mutex_unlock( &p_input->stream.stream_lock ); + if( !rtp_ChainInsert( p_access, p )) + goto again; - if( *psz_server_addr || i_server_port ) + p = p_sys->p_list; + p_sys->p_list = p_sys->p_list->p_next; + p_sys->i_last_seqno++; + if( p_sys->i_last_seqno != (uint16_t) p->i_dts ) { - msg_Err( p_input, "this UDP syntax is deprecated; the server argument will be"); - msg_Err( p_input, "ignored (%s:%d). If you wanted to enter a multicast address", - psz_server_addr, i_server_port); - msg_Err( p_input, "or local port, type : %s:@%s:%d", - *p_input->psz_access ? p_input->psz_access : "udp", - psz_server_addr, i_server_port ); + msg_Dbg( p_access, "RTP: packet(s) lost, expected %d, got %d", + p_sys->i_last_seqno, (uint16_t) p->i_dts ); + p_sys->i_last_seqno = (uint16_t) p->i_dts; + } + p->p_next = NULL; + return p; +} + +/***************************************************************************** + * BlockChoose: decide between RTP and UDP + *****************************************************************************/ +static block_t *BlockChoose( access_t *p_access ) +{ + block_t *p_block; + int i_rtp_version; + int i_CSRC_count; + int i_payload_type; - i_server_port = 0; - psz_server_addr = ""; + if( ( p_block = BlockUDP( p_access ) ) == NULL ) + return NULL; + + if( p_block->p_buffer[0] == 0x47 ) + { + msg_Dbg( p_access, "detected TS over raw UDP" ); + p_access->pf_block = BlockUDP; + return p_block; } - - msg_Dbg( p_input, "opening server=%s:%d local=%s:%d", - psz_server_addr, i_server_port, psz_bind_addr, i_bind_port ); - /* Prepare the network_socket_t structure */ - socket_desc.i_type = NETWORK_UDP; - socket_desc.psz_bind_addr = psz_bind_addr; - socket_desc.i_bind_port = i_bind_port; - socket_desc.psz_server_addr = psz_server_addr; - socket_desc.i_server_port = i_server_port; + if( p_block->i_buffer < RTP_HEADER_LEN ) + return p_block; + + /* Parse the header and make some verifications. + * See RFC 3550. */ + + i_rtp_version = ( p_block->p_buffer[0] & 0xC0 ) >> 6; + i_CSRC_count = ( p_block->p_buffer[0] & 0x0F ); + i_payload_type = ( p_block->p_buffer[1] & 0x7F ); - /* Find an appropriate network module */ - p_input->p_private = (void*) &socket_desc; - p_network = module_Need( p_input, "network", psz_network ); - free(psz_name); - if( p_network == NULL ) + if( i_rtp_version != 2 ) { - return( -1 ); + msg_Dbg( p_access, "no supported RTP header detected" ); + p_access->pf_block = BlockUDP; + return p_block; } - module_Unneed( p_input, p_network ); - - p_access_data = malloc( sizeof(input_socket_t) ); - p_input->p_access_data = (access_sys_t *)p_access_data; - if( p_access_data == NULL ) + switch( i_payload_type ) { - msg_Err( p_input, "out of memory" ); - return( -1 ); + case 33: + msg_Dbg( p_access, "detected TS over RTP" ); + p_access->psz_demux = strdup( "ts" ); + break; + + case 14: + msg_Dbg( p_access, "detected MPEG audio over RTP" ); + p_access->psz_demux = strdup( "mpga" ); + break; + + case 32: + msg_Dbg( p_access, "detected MPEG video over RTP" ); + p_access->psz_demux = strdup( "mpgv" ); + break; + + default: + msg_Dbg( p_access, "no RTP header detected" ); + p_access->pf_block = BlockUDP; + return p_block; } - p_access_data->i_handle = socket_desc.i_handle; - p_input->i_mtu = socket_desc.i_mtu; + if( !BlockParseRTP( p_access, p_block )) return NULL; + + p_access->pf_block = BlockRTP; - return( 0 ); + return BlockPrebufferRTP( p_access, p_block ); }