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255 lines
7.4 KiB
C
255 lines
7.4 KiB
C
/* GStreamer
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* Copyright (C) 2003 Martin Soto <martinsoto@users.sourceforge.net>
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*
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* ac3_padder.c: Pad AC3 frames for use with an SPDIF interface.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <stdio.h>
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#include <string.h>
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#include "ac3_padder.h"
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#define IEC61937_DATA_TYPE_AC3 1
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struct frmsize_s
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{
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unsigned short bit_rate;
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unsigned short frm_size[3];
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};
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static const struct frmsize_s frmsizecod_tbl[64] = {
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{32, {64, 69, 96}},
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{32, {64, 70, 96}},
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{40, {80, 87, 120}},
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{40, {80, 88, 120}},
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{48, {96, 104, 144}},
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{48, {96, 105, 144}},
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{56, {112, 121, 168}},
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{56, {112, 122, 168}},
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{64, {128, 139, 192}},
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{64, {128, 140, 192}},
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{80, {160, 174, 240}},
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{80, {160, 175, 240}},
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{96, {192, 208, 288}},
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{96, {192, 209, 288}},
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{112, {224, 243, 336}},
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{112, {224, 244, 336}},
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{128, {256, 278, 384}},
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{128, {256, 279, 384}},
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{160, {320, 348, 480}},
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{160, {320, 349, 480}},
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{192, {384, 417, 576}},
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{192, {384, 418, 576}},
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{224, {448, 487, 672}},
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{224, {448, 488, 672}},
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{256, {512, 557, 768}},
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{256, {512, 558, 768}},
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{320, {640, 696, 960}},
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{320, {640, 697, 960}},
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{384, {768, 835, 1152}},
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{384, {768, 836, 1152}},
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{448, {896, 975, 1344}},
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{448, {896, 976, 1344}},
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{512, {1024, 1114, 1536}},
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{512, {1024, 1115, 1536}},
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{576, {1152, 1253, 1728}},
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{576, {1152, 1254, 1728}},
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{640, {1280, 1393, 1920}},
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{640, {1280, 1394, 1920}}
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};
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/* Go one byte forward in the input buffer. */
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#define ac3p_in_fw(padder) ((padder)->in_ptr++, (padder)->remaining--)
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/* Go one byte forward in the output buffer. */
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#define ac3p_out_fw(padder) ((padder)->out_ptr++, (padder)->bytes_to_copy--)
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/**
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* ac3p_init:
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* @padder: The padder structure to initialize.
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*
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* Initializes an AC3 stream padder. This structure can be
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* subsequently used to parse an AC3 stream and convert it to IEC958
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* (S/PDIF) padded packets.
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*/
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extern void
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ac3p_init (ac3_padder * padder)
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{
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const char sync[4] = { 0x72, 0xF8, 0x1F, 0x4E };
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padder->state = AC3P_STATE_SYNC1;
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/* No material to read yet. */
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padder->remaining = 0;
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/* Initialize the sync bytes in the frame. */
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memcpy (padder->frame.header, sync, 4);
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}
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/**
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* ac3_push_data:
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* @padder: The padder structure.
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* @data: A pointer to a buffer with new data to parse. This should
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* correspond to a new piece of a stream containing raw AC3 data.
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* @size: The number of available bytes in the buffer.
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*
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* Pushes a new buffer of data to be parsed by the ac3 padder. The
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* ac3_parse() function will actually parse the data and report when
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* new frames are found. This funcion should only be called once at
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* the beginning of the parsing process, or when the ac3_parse()
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* function returns the %AC3P_EVENT_PUSH event.
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*/
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extern void
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ac3p_push_data (ac3_padder * padder, guchar * data, guint size)
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{
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padder->in_ptr = data;
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padder->remaining = size;
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}
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/**
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* ac3p_parse:
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* @padder: The padder structure.
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*
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* Parses the bytes already pushed into the padder structure (see
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* ac3p_push_data()) and returns an event value depending on the
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* results of the parsing.
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*
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* Returns: %AC3P_EVENT_FRAME to indicate that a new AC3 was found and
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* padded for IEC958 transmission. This frame can be read inmediatly
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* with ac3p_frame(). %AC3P_EVENT_PUSH to indicate that new data from
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* the input stream must be pushed into the padder using
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* ac3p_push_data(). This function should be called again after
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* pushing the data.
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*/
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extern int
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ac3p_parse (ac3_padder * padder)
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{
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while (padder->remaining > 0) {
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switch (padder->state) {
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case AC3P_STATE_SYNC1:
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if (*(padder->in_ptr) == 0x0b) {
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/* The first sync byte was found. Go to the next state. */
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padder->frame.sync_byte1 = 0x0b;
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padder->state = AC3P_STATE_SYNC2;
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}
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ac3p_in_fw (padder);
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break;
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case AC3P_STATE_SYNC2:
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if (*(padder->in_ptr) == 0x77) {
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/* The second sync byte was seen right after the first. Go to
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the next state. */
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padder->frame.sync_byte2 = 0x77;
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padder->state = AC3P_STATE_HEADER;
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/* Skip one byte. */
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ac3p_in_fw (padder);
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/* Prepare for reading the header. */
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padder->out_ptr = (guchar *) & (padder->frame.crc1);
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/* Discount the 2 sync bytes from the header size. */
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padder->bytes_to_copy = AC3P_AC3_HEADER_SIZE - 2;
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} else {
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/* The second sync byte was not seen. Go back to the
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first state. */
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padder->state = AC3P_STATE_SYNC1;
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}
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break;
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case AC3P_STATE_HEADER:
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if (padder->bytes_to_copy > 0) {
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/* Copy one byte. */
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*(padder->out_ptr) = *(padder->in_ptr);
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ac3p_in_fw (padder);
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ac3p_out_fw (padder);
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} else {
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int fscod;
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/* The header is ready: */
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fscod = (padder->frame.code >> 6) & 0x03;
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/* Calculate the frame size. */
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padder->ac3_frame_size =
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2 * frmsizecod_tbl[padder->frame.code & 0x3f].frm_size[fscod];
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/* Set up the IEC header. */
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if (padder->ac3_frame_size > 0) {
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padder->frame.header[4] = IEC61937_DATA_TYPE_AC3;
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} else {
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/* Don't know what it is, better be careful. */
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padder->state = AC3P_STATE_SYNC1;
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break;
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}
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padder->frame.header[5] = 0x00;
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padder->frame.header[6] = (padder->ac3_frame_size * 8) & 0xFF;
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padder->frame.header[7] = ((padder->ac3_frame_size * 8) >> 8) & 0xFF;
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/* Prepare for reading the body. */
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padder->bytes_to_copy = padder->ac3_frame_size - AC3P_AC3_HEADER_SIZE;
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padder->state = AC3P_STATE_CONTENT;
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}
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break;
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case AC3P_STATE_CONTENT:
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if (padder->bytes_to_copy > 0) {
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/* Copy one byte. */
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*(padder->out_ptr) = *(padder->in_ptr);
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ac3p_in_fw (padder);
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ac3p_out_fw (padder);
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} else {
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guint16 *ptr, i;
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/* Frame ready. Prepare for output: */
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/* Zero the non AC3 portion of the padded frame. */
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memset (&(padder->frame.sync_byte1) + padder->ac3_frame_size, 0,
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AC3P_IEC_FRAME_SIZE - AC3P_IEC_HEADER_SIZE -
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padder->ac3_frame_size);
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/* Fix the byte order in the AC3 portion: */
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ptr = (guint16 *) & (padder->frame.sync_byte1);
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i = padder->ac3_frame_size / 2;
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while (i > 0) {
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*ptr = GUINT16_TO_BE (*ptr);
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ptr++;
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i--;
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}
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/* Start over again. */
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padder->state = AC3P_STATE_SYNC1;
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return AC3P_EVENT_FRAME;
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}
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break;
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}
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}
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return AC3P_EVENT_PUSH;
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}
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