yading@10: /*
yading@10:  * Copyright (c) 2012 Justin Ruggles
yading@10:  *
yading@10:  * This file is part of Libav.
yading@10:  *
yading@10:  * Libav is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * Libav is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with Libav; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file
yading@10:  * Vorbis audio parser
yading@10:  *
yading@10:  * Determines the duration for each packet.
yading@10:  */
yading@10: 
yading@10: #include "get_bits.h"
yading@10: #include "parser.h"
yading@10: #include "xiph.h"
yading@10: #include "vorbis_parser.h"
yading@10: 
yading@10: static int parse_id_header(AVCodecContext *avctx, VorbisParseContext *s,
yading@10:                            const uint8_t *buf, int buf_size)
yading@10: {
yading@10:     /* Id header should be 30 bytes */
yading@10:     if (buf_size < 30) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Id header is too short\n");
yading@10:         return AVERROR_INVALIDDATA;
yading@10:     }
yading@10: 
yading@10:     /* make sure this is the Id header */
yading@10:     if (buf[0] != 1) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Wrong packet type in Id header\n");
yading@10:         return AVERROR_INVALIDDATA;
yading@10:     }
yading@10: 
yading@10:     /* check for header signature */
yading@10:     if (memcmp(&buf[1], "vorbis", 6)) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Invalid packet signature in Id header\n");
yading@10:         return AVERROR_INVALIDDATA;
yading@10:     }
yading@10: 
yading@10:     if (!(buf[29] & 0x1)) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Invalid framing bit in Id header\n");
yading@10:         return AVERROR_INVALIDDATA;
yading@10:     }
yading@10: 
yading@10:     s->blocksize[0] = 1 << (buf[28] & 0xF);
yading@10:     s->blocksize[1] = 1 << (buf[28] >>  4);
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static int parse_setup_header(AVCodecContext *avctx, VorbisParseContext *s,
yading@10:                               const uint8_t *buf, int buf_size)
yading@10: {
yading@10:     GetBitContext gb, gb0;
yading@10:     uint8_t *rev_buf;
yading@10:     int i, ret = 0;
yading@10:     int got_framing_bit, mode_count, got_mode_header, last_mode_count = 0;
yading@10: 
yading@10:     /* avoid overread */
yading@10:     if (buf_size < 7) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Setup header is too short\n");
yading@10:         return AVERROR_INVALIDDATA;
yading@10:     }
yading@10: 
yading@10:     /* make sure this is the Setup header */
yading@10:     if (buf[0] != 5) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Wrong packet type in Setup header\n");
yading@10:         return AVERROR_INVALIDDATA;
yading@10:     }
yading@10: 
yading@10:     /* check for header signature */
yading@10:     if (memcmp(&buf[1], "vorbis", 6)) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Invalid packet signature in Setup header\n");
yading@10:         return AVERROR_INVALIDDATA;
yading@10:     }
yading@10: 
yading@10:     /* reverse bytes so we can easily read backwards with get_bits() */
yading@10:     if (!(rev_buf = av_malloc(buf_size))) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Out of memory\n");
yading@10:         return AVERROR(ENOMEM);
yading@10:     }
yading@10:     for (i = 0; i < buf_size; i++)
yading@10:         rev_buf[i] = buf[buf_size - 1 - i];
yading@10:     init_get_bits(&gb, rev_buf, buf_size * 8);
yading@10: 
yading@10:     got_framing_bit = 0;
yading@10:     while (get_bits_left(&gb) > 97) {
yading@10:         if (get_bits1(&gb)) {
yading@10:             got_framing_bit = get_bits_count(&gb);
yading@10:             break;
yading@10:         }
yading@10:     }
yading@10:     if (!got_framing_bit) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Invalid Setup header\n");
yading@10:         ret = AVERROR_INVALIDDATA;
yading@10:         goto bad_header;
yading@10:     }
yading@10: 
yading@10:     /* Now we search backwards to find possible valid mode counts. This is not
yading@10:      * fool-proof because we could have false positive matches and read too
yading@10:      * far, but there isn't really any way to be sure without parsing through
yading@10:      * all the many variable-sized fields before the modes. This approach seems
yading@10:      * to work well in testing, and it is similar to how it is handled in
yading@10:      * liboggz. */
yading@10:     mode_count = 0;
yading@10:     got_mode_header = 0;
yading@10:     while (get_bits_left(&gb) >= 97) {
yading@10:         if (get_bits(&gb, 8) > 63 || get_bits(&gb, 16) || get_bits(&gb, 16))
yading@10:             break;
yading@10:         skip_bits(&gb, 1);
yading@10:         mode_count++;
yading@10:         if (mode_count > 64)
yading@10:             break;
yading@10:         gb0 = gb;
yading@10:         if (get_bits(&gb0, 6) + 1 == mode_count) {
yading@10:             got_mode_header = 1;
yading@10:             last_mode_count = mode_count;
yading@10:         }
yading@10:     }
yading@10:     if (!got_mode_header) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Invalid Setup header\n");
yading@10:         ret = AVERROR_INVALIDDATA;
yading@10:         goto bad_header;
yading@10:     }
yading@10:     /* All samples I've seen use <= 2 modes, so ask for a sample if we find
yading@10:      * more than that, as it is most likely a false positive. If we get any
yading@10:      * we may need to approach this the long way and parse the whole Setup
yading@10:      * header, but I hope very much that it never comes to that. */
yading@10:     if (last_mode_count > 2) {
yading@10:         avpriv_request_sample(avctx,
yading@10:                               "%d modes (either a false positive or a "
yading@10:                               "sample from an unknown encoder)",
yading@10:                               last_mode_count);
yading@10:     }
yading@10:     /* We're limiting the mode count to 63 so that we know that the previous
yading@10:      * block flag will be in the first packet byte. */
yading@10:     if (last_mode_count > 63) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Unsupported mode count: %d\n",
yading@10:                last_mode_count);
yading@10:         ret = AVERROR_INVALIDDATA;
yading@10:         goto bad_header;
yading@10:     }
yading@10:     s->mode_count = mode_count = last_mode_count;
yading@10:     /* Determine the number of bits required to code the mode and turn that
yading@10:      * into a bitmask to directly access the mode from the first frame byte. */
yading@10:     s->mode_mask = ((1 << (av_log2(mode_count - 1) + 1)) - 1) << 1;
yading@10:     /* The previous window flag is the next bit after the mode */
yading@10:     s->prev_mask = (s->mode_mask | 0x1) + 1;
yading@10: 
yading@10:     init_get_bits(&gb, rev_buf, buf_size * 8);
yading@10:     skip_bits_long(&gb, got_framing_bit);
yading@10:     for (i = mode_count - 1; i >= 0; i--) {
yading@10:         skip_bits_long(&gb, 40);
yading@10:         s->mode_blocksize[i] = get_bits1(&gb);
yading@10:     }
yading@10: 
yading@10: bad_header:
yading@10:     av_free(rev_buf);
yading@10:     return ret;
yading@10: }
yading@10: 
yading@10: int avpriv_vorbis_parse_extradata(AVCodecContext *avctx, VorbisParseContext *s)
yading@10: {
yading@10:     uint8_t *header_start[3];
yading@10:     int header_len[3];
yading@10:     int ret;
yading@10: 
yading@10:     s->avctx = avctx;
yading@10:     s->extradata_parsed = 1;
yading@10: 
yading@10:     if ((ret = avpriv_split_xiph_headers(avctx->extradata,
yading@10:                                          avctx->extradata_size, 30,
yading@10:                                          header_start, header_len)) < 0) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Extradata corrupt.\n");
yading@10:         return ret;
yading@10:     }
yading@10: 
yading@10:     if ((ret = parse_id_header(avctx, s, header_start[0], header_len[0])) < 0)
yading@10:         return ret;
yading@10: 
yading@10:     if ((ret = parse_setup_header(avctx, s, header_start[2], header_len[2])) < 0)
yading@10:         return ret;
yading@10: 
yading@10:     s->valid_extradata = 1;
yading@10:     s->previous_blocksize = s->blocksize[s->mode_blocksize[0]];
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: int avpriv_vorbis_parse_frame(VorbisParseContext *s, const uint8_t *buf,
yading@10:                               int buf_size)
yading@10: {
yading@10:     int duration = 0;
yading@10: 
yading@10:     if (s->valid_extradata && buf_size > 0) {
yading@10:         int mode, current_blocksize;
yading@10:         int previous_blocksize = s->previous_blocksize;
yading@10: 
yading@10:         if (buf[0] & 1) {
yading@10:             av_log(s->avctx, AV_LOG_ERROR, "Invalid packet\n");
yading@10:             return AVERROR_INVALIDDATA;
yading@10:         }
yading@10:         if (s->mode_count == 1)
yading@10:             mode = 0;
yading@10:         else
yading@10:             mode = (buf[0] & s->mode_mask) >> 1;
yading@10:         if (mode >= s->mode_count) {
yading@10:             av_log(s->avctx, AV_LOG_ERROR, "Invalid mode in packet\n");
yading@10:             return AVERROR_INVALIDDATA;
yading@10:         }
yading@10:         if(s->mode_blocksize[mode]){
yading@10:             int flag = !!(buf[0] & s->prev_mask);
yading@10:             previous_blocksize = s->blocksize[flag];
yading@10:         }
yading@10:         current_blocksize     = s->blocksize[s->mode_blocksize[mode]];
yading@10:         duration              = (previous_blocksize + current_blocksize) >> 2;
yading@10:         s->previous_blocksize = current_blocksize;
yading@10:     }
yading@10: 
yading@10:     return duration;
yading@10: }
yading@10: 
yading@10: void avpriv_vorbis_parse_reset(VorbisParseContext *s)
yading@10: {
yading@10:     if (s->valid_extradata)
yading@10:         s->previous_blocksize = s->blocksize[0];
yading@10: }
yading@10: 
yading@10: #if CONFIG_VORBIS_PARSER
yading@10: static int vorbis_parse(AVCodecParserContext *s1, AVCodecContext *avctx,
yading@10:                         const uint8_t **poutbuf, int *poutbuf_size,
yading@10:                         const uint8_t *buf, int buf_size)
yading@10: {
yading@10:     VorbisParseContext *s = s1->priv_data;
yading@10:     int duration;
yading@10: 
yading@10:     if (!s->extradata_parsed && avctx->extradata && avctx->extradata_size)
yading@10:         if (avpriv_vorbis_parse_extradata(avctx, s))
yading@10:             goto end;
yading@10: 
yading@10:     if ((duration = avpriv_vorbis_parse_frame(s, buf, buf_size)) >= 0)
yading@10:         s1->duration = duration;
yading@10: 
yading@10: end:
yading@10:     /* always return the full packet. this parser isn't doing any splitting or
yading@10:        combining, only packet analysis */
yading@10:     *poutbuf      = buf;
yading@10:     *poutbuf_size = buf_size;
yading@10:     return buf_size;
yading@10: }
yading@10: 
yading@10: AVCodecParser ff_vorbis_parser = {
yading@10:     .codec_ids      = { AV_CODEC_ID_VORBIS },
yading@10:     .priv_data_size = sizeof(VorbisParseContext),
yading@10:     .parser_parse   = vorbis_parse,
yading@10: };
yading@10: #endif /* CONFIG_VORBIS_PARSER */