kopia lustrzana https://github.com/F5OEO/tstools
136 wiersze
5.1 KiB
C
136 wiersze
5.1 KiB
C
/*
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* Definitions for working with H.222 Transport Stream packets
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*
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* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is the MPEG TS, PS and ES tools.
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*
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* The Initial Developer of the Original Code is Amino Communications Ltd.
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* Portions created by the Initial Developer are Copyright (C) 2008
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Amino Communications Ltd, Swavesey, Cambridge UK
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*
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* ***** END LICENSE BLOCK *****
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*/
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#ifndef _ts_defns
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#define _ts_defns
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#include "compat.h"
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// Transport Stream packets are always the same size
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#define TS_PACKET_SIZE 188
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// When we are putting data into a TS packet, we need the first four
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// bytes for heading information, which means that we will have at most
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// 184 bytes for our payload
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#define MAX_TS_PAYLOAD_SIZE (TS_PACKET_SIZE-4)
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// ------------------------------------------------------------
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// Support for PCR read-ahead buffering
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// Basically, always ensure that we know have read both the
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// previous and the next PCR, so we can calculate the actual
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// PCR for each packet between.
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// Let's guess for a maximum number of TS entries we're likely to need
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// to be able to hold...
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//
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// XXX But whatever number we guess here will be too small for some
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// XXX streams, or so big it's really quite over the top for most
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// XXX (and more than I'd like). So maybe we should have something
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// XXX that's likely to cope for most streams, and we should (ideally)
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// XXX have a way for the user to set the size with a swich, but also
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// XXX (perhaps) we should allow the reader to continue (using the last
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// XXX calculated rate) if we can't read ahead? Or perhaps having the
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// XXX switch is enough, for the nonce... Or maybe we should allow the
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// XXX buffer to grow (on demand, within some sort of reason) if it
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// XXX needs to.
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#define PCR_READ_AHEAD_SIZE 20000 // a made-up number
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struct _ts_pcr_buffer
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{
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byte TS_buffer[PCR_READ_AHEAD_SIZE][TS_PACKET_SIZE];
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// For convenience (since we'll already have calculated this once),
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// remember each packets PID
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uint32_t TS_buffer_pids[PCR_READ_AHEAD_SIZE];
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// And the PCR PID we're looking for (we have to assume that's fairly
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// static, or we couldn't do read-aheads and interpolations)
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uint32_t TS_buffer_pcr_pid;
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// The number of TS entries we've got therein, the *last* of which
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// has a PCR
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int TS_buffer_len;
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// Which TS packet we should read next...
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int TS_buffer_next;
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// The PCR of that last entry
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uint64_t TS_buffer_end_pcr;
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// And the PCR of the *previous* last entry
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uint64_t TS_buffer_prev_pcr;
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// From which, we can deduce the time per packet
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uint64_t TS_buffer_time_per_TS;
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// For diagnostic purposes, the sequence number of TS_buffer[0]
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// (and thus, of the overall read-ahead buffer) in the overall file
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int TS_buffer_posn;
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// Did we read an EOF before finding a "second" PCR?
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// (perhaps we should instead call this "TS_playing_out", but that's
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// less directly named from how we set it)
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int TS_had_EOF;
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};
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typedef struct _ts_pcr_buffer *TS_pcr_buffer_p;
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#define SIZEOF_TS_PCR_BUFFER sizeof(struct _ts_pcr_buffer)
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// ------------------------------------------------------------
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// The number of TS packets to read ahead
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#define TS_READ_AHEAD_COUNT 7 // aim for multiple of block boundary -- used to be 50
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// Thus the number of bytes to read ahead
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#define TS_READ_AHEAD_BYTES TS_READ_AHEAD_COUNT*TS_PACKET_SIZE
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// A read-ahead buffer for reading TS packets.
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//
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// Note that `posn` always gives the file position of the *next* TS packet to
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// be read from the file (so after reading a TS packet with
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// `read_next_TS_packet`, the position of said packet is `posn`-TS_PACKET_SIZE)
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struct _ts_reader
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{
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int file; // the file to read from
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offset_t posn; // the position of the next-to-be-read TS packet
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void *handle; // handle to pass to read_fn and seek_fn.
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// Reader and seek functions. If these are non-NULL we call them
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// when we would call read() or seek().
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int (*read_fn)(void *, byte *, size_t);
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int (*seek_fn)(void *, offset_t);
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byte read_ahead[TS_READ_AHEAD_COUNT*TS_PACKET_SIZE];
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byte *read_ahead_ptr; // location of next packet in said array
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byte *read_ahead_end; // pointer just after the end of `read_ahead`
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// If we are doing PCR read-ahead (so we have exact PCR values for our
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// TS packets), then we also need:
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TS_pcr_buffer_p pcrbuf;
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};
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typedef struct _ts_reader *TS_reader_p;
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#define SIZEOF_TS_READER sizeof(struct _ts_reader)
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#endif // _ts_defns
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// Local Variables:
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// tab-width: 8
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// indent-tabs-mode: nil
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// c-basic-offset: 2
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// End:
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// vim: set tabstop=8 shiftwidth=2 expandtab:
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