MLP/TrueHD parser

Patch by Ian Caulfield, ian D caulfield <at> gmail D com
Thread: [PATCH] MLP/TrueHD decoder, 12 Oct 14:26

Originally committed as revision 11109 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 307 insertions, 0 deletions

diff --git a/libavcodec/mlp_parser.c b/libavcodec/mlp_parser.c
new file mode 100644
index 0000000000..c946fcf743
--- /dev/null
+++ b/libavcodec/mlp_parser.c
@@ -0,0 +1,307 @@
+/*
+ * MLP parser
+ * Copyright (c) 2007 Ian Caulfield
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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 GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file mlp_parser.c
+ * MLP parser
+ */
+
+#include "bitstream.h"
+#include "parser.h"
+#include "crc.h"
+#include "mlp_parser.h"
+
+static const uint8_t mlp_quants[16] = {
+    16, 20, 24, 0, 0, 0, 0, 0,
+     0,  0,  0, 0, 0, 0, 0, 0,
+};
+
+static const uint8_t mlp_channels[32] = {
+    1, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 4, 5, 4,
+    5, 6, 5, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+};
+
+static const uint8_t thd_chancount[13] = {
+//  LR    C   LFE  LRs LRvh  LRc LRrs  Cs   Ts  LRsd  LRw  Cvh  LFE2
+     2,   1,   1,   2,   2,   2,   2,   1,   1,   2,   2,   1,   1
+};
+
+static int mlp_samplerate(int in)
+{
+    if (in == 0xF)
+        return 0;
+
+    return (in & 8 ? 44100 : 48000) << (in & 7) ;
+}
+
+static int truehd_channels(int chanmap)
+{
+    int channels = 0, i;
+
+    for (i = 0; i < 13; i++)
+        channels += thd_chancount[i] * ((chanmap >> i) & 1);
+
+    return channels;
+}
+
+static int crc_init = 0;
+static AVCRC crc_2D[1024];
+
+/** MLP uses checksums that seem to be based on the standard CRC algorithm,
+ *  but not (in implementation terms, the table lookup and XOR are reversedi).
+ *  We can implement this behaviour using a standard av_crc on all but the
+ *  last element, then XOR that with the last element.
+ */
+
+static uint16_t mlp_checksum16(const uint8_t *buf, unsigned int buf_size)
+{
+    uint16_t crc;
+
+    if (!crc_init) {
+        av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D));
+        crc_init = 1;
+    }
+
+    crc = av_crc(crc_2D, 0, buf, buf_size - 2);
+    crc ^= AV_RL16(buf + buf_size - 2);
+    return crc;
+}
+
+/** Read a major sync info header - contains high level information about
+ *  the stream - sample rate, channel arrangement etc. Most of this
+ *  information is not actually necessary for decoding, only for playback.
+ */
+
+int ff_mlp_read_major_sync(void *log, MLPHeaderInfo *mh, const uint8_t *buf,
+                           unsigned int buf_size)
+{
+    GetBitContext gb;
+    int ratebits;
+    uint16_t checksum;
+
+    if (buf_size < 28) {
+        av_log(log, AV_LOG_ERROR, "Packet too short, unable to read major sync\n");
+        return -1;
+    }
+
+    checksum = mlp_checksum16(buf, 26);
+    if (checksum != AV_RL16(buf+26)) {
+        av_log(log, AV_LOG_ERROR, "Major sync info header checksum error\n");
+        return -1;
+    }
+
+    init_get_bits(&gb, buf, buf_size * 8);
+
+    if (get_bits_long(&gb, 24) != 0xf8726f) /* Sync words */
+        return -1;
+
+    mh->stream_type = get_bits(&gb, 8);
+
+    if (mh->stream_type == 0xbb) {
+        mh->group1_bits = mlp_quants[get_bits(&gb, 4)];
+        mh->group2_bits = mlp_quants[get_bits(&gb, 4)];
+
+        ratebits = get_bits(&gb, 4);
+        mh->group1_samplerate = mlp_samplerate(ratebits);
+        mh->group2_samplerate = mlp_samplerate(get_bits(&gb, 4));
+
+        skip_bits(&gb, 11);
+
+        mh->channels_mlp = get_bits(&gb, 5);
+    } else if (mh->stream_type == 0xba) {
+        mh->group1_bits = 24; // TODO: Is this information actually conveyed anywhere?
+        mh->group2_bits = 0;
+
+        ratebits = get_bits(&gb, 4);
+        mh->group1_samplerate = mlp_samplerate(ratebits);
+        mh->group2_samplerate = 0;
+
+        skip_bits(&gb, 8);
+
+        mh->channels_thd_stream1 = get_bits(&gb, 5);
+
+        skip_bits(&gb, 2);
+
+        mh->channels_thd_stream2 = get_bits(&gb, 13);
+    } else
+        return -1;
+
+    mh->access_unit_size = 40 << (ratebits & 7);
+    mh->access_unit_size_pow2 = 64 << (ratebits & 7);
+
+    skip_bits_long(&gb, 48);
+
+    mh->is_vbr = get_bits1(&gb);
+
+    mh->peak_bitrate = (get_bits(&gb, 15) * mh->group1_samplerate + 8) >> 4;
+
+    mh->num_substreams = get_bits(&gb, 4);
+
+    skip_bits_long(&gb, 4 + 11 * 8);
+
+    return 0;
+}
+
+typedef struct MLPParseContext
+{
+    ParseContext pc;
+
+    int bytes_left;
+
+    int in_sync;
+
+    int num_substreams;
+} MLPParseContext;
+
+static int mlp_parse(AVCodecParserContext *s,
+                     AVCodecContext *avctx,
+                     const uint8_t **poutbuf, int *poutbuf_size,
+                     const uint8_t *buf, int buf_size)
+{
+    MLPParseContext *mp = s->priv_data;
+    int sync_present;
+    uint8_t parity_bits;
+    int next;
+    int i, p = 0;
+
+    *poutbuf_size = 0;
+    if (buf_size == 0)
+        return 0;
+
+    if (!mp->in_sync) {
+        // Not in sync - find a major sync header
+
+        for (i = 0; i < buf_size; i++) {
+            mp->pc.state = (mp->pc.state << 8) | buf[i];
+            if ((mp->pc.state & 0xfffffffe) == 0xf8726fba) {
+                mp->in_sync = 1;
+                mp->bytes_left = 0;
+                break;
+            }
+        }
+
+        if (!mp->in_sync) {
+            ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
+            return buf_size;
+        }
+
+        ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size);
+
+        return i - 7;
+    }
+
+    if (mp->bytes_left == 0) {
+        // Find length of this packet
+
+        /* Copy overread bytes from last frame into buffer. */
+        for(; mp->pc.overread>0; mp->pc.overread--) {
+            mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++];
+        }
+
+        if (mp->pc.index + buf_size < 2) {
+            ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
+            return buf_size;
+        }
+
+        mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8)
+                       |  (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]);
+        mp->bytes_left = (mp->bytes_left & 0xfff) * 2;
+        mp->bytes_left -= mp->pc.index;
+    }
+
+    next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left;
+
+    if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) {
+        mp->bytes_left -= buf_size;
+        return buf_size;
+    }
+
+    mp->bytes_left = 0;
+
+    sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
+
+    if (!sync_present) {
+        // First nibble of a frame is a parity check of the first few nibbles
+        // Only check when this isn't a sync frame - syncs have a checksum
+
+        parity_bits = 0;
+        for (i = 0; i <= mp->num_substreams; i++) {
+            parity_bits ^= buf[p++];
+            parity_bits ^= buf[p++];
+
+            if (i == 0 || buf[p-2] & 0x80) {
+                parity_bits ^= buf[p++];
+                parity_bits ^= buf[p++];
+            }
+        }
+
+        if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
+            av_log(avctx, AV_LOG_INFO, "mlpparse: parity check failed\n");
+            goto lost_sync;
+        }
+    } else {
+        MLPHeaderInfo mh;
+
+        if (ff_mlp_read_major_sync(avctx, &mh, buf + 4, buf_size - 4) < 0)
+            goto lost_sync;
+
+#ifdef CONFIG_AUDIO_NONSHORT
+        avctx->bits_per_sample = mh.group1_bits;
+        if (avctx->bits_per_sample > 16)
+            avctx->sample_fmt = SAMPLE_FMT_S32;
+#endif
+        avctx->sample_rate = mh.group1_samplerate;
+        avctx->frame_size = mh.access_unit_size;
+
+        if (mh.stream_type == 0xbb) {
+            /* MLP stream */
+            avctx->channels = mlp_channels[mh.channels_mlp];
+        } else { /* mh.stream_type == 0xba */
+            /* TrueHD stream */
+            if (mh.channels_thd_stream2)
+                avctx->channels = truehd_channels(mh.channels_thd_stream2);
+            else
+                avctx->channels = truehd_channels(mh.channels_thd_stream1);
+        }
+
+        if (!mh.is_vbr) /* Stream is CBR */
+            avctx->bit_rate = mh.peak_bitrate;
+
+        mp->num_substreams = mh.num_substreams;
+    }
+
+    *poutbuf = buf;
+    *poutbuf_size = buf_size;
+
+    return next;
+
+lost_sync:
+    mp->in_sync = 0;
+    return -1;
+}
+
+AVCodecParser mlp_parser = {
+    { CODEC_ID_MLP },
+    sizeof(MLPParseContext),
+    NULL,
+    mlp_parse,
+    NULL,
+};