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https://gitlab.freedesktop.org/gstreamer/gstreamer.git
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5e1a50c7f0
Original commit message from CVS: Various changes to AC3->IEC958 framer. Mostly to make our IEC958 headers more accurate, and to check AC3 checksums (both of them in each frame), and dump the frame (as a probable sync failure) if they don't match. General code cleanup, improved comments. Changed to not construct the header backwards, and not byteswap everything else. If we end up needing to do little-endian output, we should swap in the element doing the output (AC3 is big-endian).
390 lines
13 KiB
C
390 lines
13 KiB
C
/* GStreamer
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* Copyright (C) 2003, 2004 Martin Soto <martinsoto@users.sourceforge.net>
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* 2005 Michael Smith <msmith@fluendo.com>
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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., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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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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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[] = {
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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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static const guint16 ac3_crc_lut[256] = {
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0x0000, 0x8005, 0x800f, 0x000a, 0x801b, 0x001e, 0x0014, 0x8011,
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0x8033, 0x0036, 0x003c, 0x8039, 0x0028, 0x802d, 0x8027, 0x0022,
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0x8063, 0x0066, 0x006c, 0x8069, 0x0078, 0x807d, 0x8077, 0x0072,
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0x0050, 0x8055, 0x805f, 0x005a, 0x804b, 0x004e, 0x0044, 0x8041,
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0x80c3, 0x00c6, 0x00cc, 0x80c9, 0x00d8, 0x80dd, 0x80d7, 0x00d2,
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0x00f0, 0x80f5, 0x80ff, 0x00fa, 0x80eb, 0x00ee, 0x00e4, 0x80e1,
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0x00a0, 0x80a5, 0x80af, 0x00aa, 0x80bb, 0x00be, 0x00b4, 0x80b1,
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0x8093, 0x0096, 0x009c, 0x8099, 0x0088, 0x808d, 0x8087, 0x0082,
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0x8183, 0x0186, 0x018c, 0x8189, 0x0198, 0x819d, 0x8197, 0x0192,
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0x01b0, 0x81b5, 0x81bf, 0x01ba, 0x81ab, 0x01ae, 0x01a4, 0x81a1,
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0x01e0, 0x81e5, 0x81ef, 0x01ea, 0x81fb, 0x01fe, 0x01f4, 0x81f1,
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0x81d3, 0x01d6, 0x01dc, 0x81d9, 0x01c8, 0x81cd, 0x81c7, 0x01c2,
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0x0140, 0x8145, 0x814f, 0x014a, 0x815b, 0x015e, 0x0154, 0x8151,
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0x8173, 0x0176, 0x017c, 0x8179, 0x0168, 0x816d, 0x8167, 0x0162,
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0x8123, 0x0126, 0x012c, 0x8129, 0x0138, 0x813d, 0x8137, 0x0132,
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0x0110, 0x8115, 0x811f, 0x011a, 0x810b, 0x010e, 0x0104, 0x8101,
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0x8303, 0x0306, 0x030c, 0x8309, 0x0318, 0x831d, 0x8317, 0x0312,
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0x0330, 0x8335, 0x833f, 0x033a, 0x832b, 0x032e, 0x0324, 0x8321,
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0x0360, 0x8365, 0x836f, 0x036a, 0x837b, 0x037e, 0x0374, 0x8371,
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0x8353, 0x0356, 0x035c, 0x8359, 0x0348, 0x834d, 0x8347, 0x0342,
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0x03c0, 0x83c5, 0x83cf, 0x03ca, 0x83db, 0x03de, 0x03d4, 0x83d1,
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0x83f3, 0x03f6, 0x03fc, 0x83f9, 0x03e8, 0x83ed, 0x83e7, 0x03e2,
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0x83a3, 0x03a6, 0x03ac, 0x83a9, 0x03b8, 0x83bd, 0x83b7, 0x03b2,
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0x0390, 0x8395, 0x839f, 0x039a, 0x838b, 0x038e, 0x0384, 0x8381,
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0x0280, 0x8285, 0x828f, 0x028a, 0x829b, 0x029e, 0x0294, 0x8291,
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0x82b3, 0x02b6, 0x02bc, 0x82b9, 0x02a8, 0x82ad, 0x82a7, 0x02a2,
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0x82e3, 0x02e6, 0x02ec, 0x82e9, 0x02f8, 0x82fd, 0x82f7, 0x02f2,
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0x02d0, 0x82d5, 0x82df, 0x02da, 0x82cb, 0x02ce, 0x02c4, 0x82c1,
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0x8243, 0x0246, 0x024c, 0x8249, 0x0258, 0x825d, 0x8257, 0x0252,
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0x0270, 0x8275, 0x827f, 0x027a, 0x826b, 0x026e, 0x0264, 0x8261,
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0x0220, 0x8225, 0x822f, 0x022a, 0x823b, 0x023e, 0x0234, 0x8231,
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0x8213, 0x0216, 0x021c, 0x8219, 0x0208, 0x820d, 0x8207, 0x0202
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};
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typedef guint16 ac3_crc_state;
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static void
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ac3_crc_init (ac3_crc_state * state)
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{
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*state = 0;
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}
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static void
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ac3_crc_update (ac3_crc_state * state, guint8 * data, guint32 num_bytes)
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{
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int i;
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for (i = 0; i < num_bytes; i++)
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*state = ac3_crc_lut[data[i] ^ (*state >> 8)] ^ (*state << 8);
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}
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static int
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ac3_crc_validate (ac3_crc_state * state)
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{
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return (*state == 0);
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}
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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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void
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ac3p_init (ac3_padder * padder)
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{
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const char sync[4] = { 0xF8, 0x72, 0x4E, 0x1F };
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padder->state = AC3P_STATE_SYNC1;
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padder->skipped = 0;
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/* No material to read yet. */
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padder->buffer = NULL;
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padder->buffer_end = 0;
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padder->buffer_cur = 0;
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padder->buffer_size = 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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void
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ac3p_clear (ac3_padder * padder)
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{
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g_free (padder->buffer);
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}
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static void
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resync (ac3_padder * padder, int offset, int skipped)
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{
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padder->buffer_cur -= offset;
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padder->state = AC3P_STATE_SYNC1;
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padder->skipped += skipped;
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/* We don't want our buffer to grow unboundedly if we fail to find sync, but
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* nor do we want to do this every time we call resync() */
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if (padder->buffer_cur > 4096) {
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memmove (padder->buffer, padder->buffer + padder->buffer_cur,
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padder->buffer_end - padder->buffer_cur);
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padder->buffer_end -= padder->buffer_cur;
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padder->buffer_cur = 0;
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}
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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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if (padder->buffer_end + size > padder->buffer_size) {
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padder->buffer_size = padder->buffer_end + size;
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padder->buffer = g_realloc (padder->buffer, padder->buffer_size);
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}
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memcpy (padder->buffer + padder->buffer_end, data, size);
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padder->buffer_end += 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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* Note that the returned data (which naturally comes in 16 bit sub-frames) is
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* big-endian, and may need to be byte-swapped for little-endian output.
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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->buffer_cur < padder->buffer_end) {
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switch (padder->state) {
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case AC3P_STATE_SYNC1:
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if (padder->buffer[padder->buffer_cur++] == 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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} else
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resync (padder, 0, 1);
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break;
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case AC3P_STATE_SYNC2:
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if (padder->buffer[padder->buffer_cur++] == 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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/* 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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resync (padder, 0, 2);
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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->buffer[padder->buffer_cur++];
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padder->bytes_to_copy--;
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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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/* fscod == 3 is a reserved code, we're not meant to do playback in
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* this case. frmsizecod being out-of-range (there are 38 entries)
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* doesn't appear to be well-defined, but treat the same.
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* The likely cause of both of these is false sync, so skip back to
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* just in front of the previous sync word and start looking again.
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*/
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if (fscod == 3 || (padder->frame.code & 0x3f) >= 38) {
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resync (padder, AC3P_AC3_HEADER_SIZE - 2, 2);
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continue;
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}
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/* Calculate the frame size (in 16 bit units). */
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padder->ac3_frame_size =
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frmsizecod_tbl[padder->frame.code & 0x3f].frm_size[fscod];
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/* Prepare for reading the body. */
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padder->bytes_to_copy = padder->ac3_frame_size * 2
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- 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->buffer[padder->buffer_cur++];
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padder->bytes_to_copy--;
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} else {
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int framesize;
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int crclen1, crclen2;
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guint8 *tmp;
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ac3_crc_state state;
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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 * 2, 0,
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AC3P_IEC_FRAME_SIZE - AC3P_IEC_HEADER_SIZE -
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padder->ac3_frame_size * 2);
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/* Now checking the two CRCs. If either fails, then we re-feed all
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* the data starting immediately after the 16-bit syncword (which we
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* can now assume was a false sync) */
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/* Length of CRC1 is defined as
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truncate(framesize/2) + truncate(framesize/8)
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units (each of which is 16 bit, as is 'framesize'), but this
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includes the syncword, which is NOT calculated as part of
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the CRC.
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*/
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framesize = padder->ac3_frame_size;
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crclen1 = (framesize / 2 + framesize / 8) * 2 - 2;
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tmp = (guint8 *) (&(padder->frame.crc1));
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ac3_crc_init (&state);
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ac3_crc_update (&state, tmp, crclen1);
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if (!ac3_crc_validate (&state)) {
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/* Rewind current stream pointer to immediately following the last
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* attempted sync point, then continue parsing in initial state */
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resync (padder, padder->ac3_frame_size - 2, 2);
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continue;
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}
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/* Now check CRC2, which covers the entire frame other than the
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* 16-bit syncword */
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crclen2 = padder->ac3_frame_size * 2 - 2;
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ac3_crc_init (&state);
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ac3_crc_update (&state, tmp, crclen2);
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if (!ac3_crc_validate (&state)) {
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/* Rewind current stream pointer to immediately following the last
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* attempted sync point, then continue parsing in initial state */
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resync (padder, padder->ac3_frame_size - 2, 2);
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continue;
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}
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/* Now set up the rest of the IEC header (we already filled in the
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32 bit sync word. */
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/* Byte 5 has:
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bits 0-4: data type dependent. For AC3, the bottom 3 of these bits
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are copied from the AC3 frame (bsmod value), the top 2
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bits are reserved, and set to zero.
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bits 5-7: data stream number. We only do one data stream, so it's
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zero.
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*/
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padder->frame.header[4] = padder->frame.bsidmod & 0x07;
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/* Byte 6:
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bits 0-4: data type. 1 for AC3.
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bits 5-6: reserved, zero.
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bit 7: error_flag. Zero if frame contains no errors
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*/
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padder->frame.header[5] = 1; /* AC3 is defined as datatype 1 */
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/* Now, 16 bit frame size, in bits. */
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padder->frame.header[6] = ((padder->ac3_frame_size * 16) >> 8) & 0xFF;
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padder->frame.header[7] = (padder->ac3_frame_size * 16) & 0xFF;
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/* We're done, reset state and signal that we have a frame */
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padder->skipped = 0;
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padder->state = AC3P_STATE_SYNC1;
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memmove (padder->buffer, padder->buffer + padder->buffer_cur,
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padder->buffer_end - padder->buffer_cur);
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padder->buffer_end -= padder->buffer_cur;
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padder->buffer_cur = 0;
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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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