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ffmpeg / libavcodec / flac_parser.c @ 2912e87a

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1
/*
2
 * FLAC parser
3
 * Copyright (c) 2010 Michael Chinen
4
 *
5
 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav 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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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
21

    
22
/**
23
 * @file
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 * FLAC parser
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 *
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 * The FLAC parser buffers input until FLAC_MIN_HEADERS has been found.
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 * Each time it finds and verifies a CRC-8 header it sees which of the
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 * FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer
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 * that ends at the newly found header.
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 * Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of it's crc-verified
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 * children, penalized by changes in sample rate, frame number, etc.
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 * The parser returns the frame with the highest score.
33
 **/
34

    
35
#include "libavutil/crc.h"
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#include "libavutil/fifo.h"
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#include "bytestream.h"
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#include "parser.h"
39
#include "flac.h"
40

    
41
/** maximum number of adjacent headers that compare CRCs against each other   */
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#define FLAC_MAX_SEQUENTIAL_HEADERS 3
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/** minimum number of headers buffered and checked before returning frames    */
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#define FLAC_MIN_HEADERS 10
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/** estimate for average size of a FLAC frame                                 */
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#define FLAC_AVG_FRAME_SIZE 8192
47

    
48
/** scoring settings for score_header */
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#define FLAC_HEADER_BASE_SCORE        10
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#define FLAC_HEADER_CHANGED_PENALTY   7
51
#define FLAC_HEADER_CRC_FAIL_PENALTY  50
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#define FLAC_HEADER_NOT_PENALIZED_YET 100000
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#define FLAC_HEADER_NOT_SCORED_YET    -100000
54

    
55
/** largest possible size of flac header */
56
#define MAX_FRAME_HEADER_SIZE 16
57

    
58
typedef struct FLACHeaderMarker {
59
    int offset;       /**< byte offset from start of FLACParseContext->buffer */
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    int *link_penalty;  /**< pointer to array of local scores between this header
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                           and the one at a distance equal array position     */
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    int max_score;    /**< maximum score found after checking each child that
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                           has a valid CRC                                    */
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    FLACFrameInfo fi; /**< decoded frame header info                          */
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    struct FLACHeaderMarker *next;       /**< next CRC-8 verified header that
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                                              immediately follows this one in
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                                              the bytestream                  */
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    struct FLACHeaderMarker *best_child; /**< following frame header with
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                                              which this frame has the best
70
                                              score with                      */
71
} FLACHeaderMarker;
72

    
73
typedef struct FLACParseContext {
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    AVCodecContext *avctx;         /**< codec context pointer for logging     */
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    FLACHeaderMarker *headers;     /**< linked-list that starts at the first
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                                        CRC-8 verified header within buffer   */
77
    FLACHeaderMarker *best_header; /**< highest scoring header within buffer  */
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    int nb_headers_found;          /**< number of headers found in the last
79
                                        flac_parse() call                     */
80
    int nb_headers_buffered;       /**< number of headers that are buffered   */
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    int best_header_valid;         /**< flag set when the parser returns junk;
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                                        if set return best_header next time   */
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    AVFifoBuffer *fifo_buf;        /**< buffer to store all data until headers
84
                                        can be verified                       */
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    int end_padded;                /**< specifies if fifo_buf's end is padded */
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    uint8_t *wrap_buf;             /**< general fifo read buffer when wrapped */
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    int wrap_buf_allocated_size;   /**< actual allocated size of the buffer   */
88
} FLACParseContext;
89

    
90
static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
91
                                 FLACFrameInfo *fi)
92
{
93
    GetBitContext gb;
94
    init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
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    return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
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}
97

    
98
/**
99
 * Non-destructive fast fifo pointer fetching
100
 * Returns a pointer from the specified offset.
101
 * If possible the pointer points within the fifo buffer.
102
 * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
103
 * buffer is used.
104
 * The pointer can be NULL.  In any case it will be reallocated to hold the size.
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 * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
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 * then the subsequent calls should pass in a different wrap_buf so as to not
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 * overwrite the contents of the previous wrap_buf.
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 * This function is based on av_fifo_generic_read, which is why there is a comment
109
 * about a memory barrier for SMP.
110
 */
111
static uint8_t* flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len,
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                               uint8_t** wrap_buf, int* allocated_size)
113
{
114
    AVFifoBuffer *f   = fpc->fifo_buf;
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    uint8_t *start    = f->rptr + offset;
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    uint8_t *tmp_buf;
117

    
118
    if (start >= f->end)
119
        start -= f->end - f->buffer;
120
    if (f->end - start >= len)
121
        return start;
122

    
123
    tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
124

    
125
    if (!tmp_buf) {
126
        av_log(fpc->avctx, AV_LOG_ERROR,
127
               "couldn't reallocate wrap buffer of size %d", len);
128
        return NULL;
129
    }
130
    *wrap_buf = tmp_buf;
131
    do {
132
        int seg_len = FFMIN(f->end - start, len);
133
        memcpy(tmp_buf, start, seg_len);
134
        tmp_buf = (uint8_t*)tmp_buf + seg_len;
135
// memory barrier needed for SMP here in theory
136

    
137
        start += seg_len - (f->end - f->buffer);
138
        len -= seg_len;
139
    } while (len > 0);
140

    
141
    return *wrap_buf;
142
}
143

    
144
/**
145
 * Return a pointer in the fifo buffer where the offset starts at until
146
 * the wrap point or end of request.
147
 * len will contain the valid length of the returned buffer.
148
 * A second call to flac_fifo_read (with new offset and len) should be called
149
 * to get the post-wrap buf if the returned len is less than the requested.
150
 **/
151
static uint8_t* flac_fifo_read(FLACParseContext *fpc, int offset, int *len)
152
{
153
    AVFifoBuffer *f   = fpc->fifo_buf;
154
    uint8_t *start    = f->rptr + offset;
155

    
156
    if (start >= f->end)
157
        start -= f->end - f->buffer;
158
    *len = FFMIN(*len, f->end - start);
159
    return start;
160
}
161

    
162
static int find_headers_search_validate(FLACParseContext *fpc, int offset)
163
{
164
    FLACFrameInfo fi;
165
    uint8_t *header_buf;
166
    int size = 0;
167
    header_buf = flac_fifo_read_wrap(fpc, offset,
168
                                     MAX_FRAME_HEADER_SIZE,
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                                     &fpc->wrap_buf,
170
                                     &fpc->wrap_buf_allocated_size);
171
    if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
172
        FLACHeaderMarker **end_handle = &fpc->headers;
173
        int i;
174

    
175
        size = 0;
176
        while (*end_handle) {
177
            end_handle = &(*end_handle)->next;
178
            size++;
179
        }
180

    
181
        *end_handle = av_mallocz(sizeof(FLACHeaderMarker));
182
        if (!*end_handle) {
183
            av_log(fpc->avctx, AV_LOG_ERROR,
184
                   "couldn't allocate FLACHeaderMarker\n");
185
            return AVERROR(ENOMEM);
186
        }
187
        (*end_handle)->fi           = fi;
188
        (*end_handle)->offset       = offset;
189
        (*end_handle)->link_penalty = av_malloc(sizeof(int) *
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                                            FLAC_MAX_SEQUENTIAL_HEADERS);
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        for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
192
            (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
193

    
194
        fpc->nb_headers_found++;
195
        size++;
196
    }
197
    return size;
198
}
199

    
200
static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
201
                               int search_start)
202

    
203
{
204
    int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
205
    uint32_t x;
206

    
207
    for (i = 0; i < mod_offset; i++) {
208
        if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
209
            size = find_headers_search_validate(fpc, search_start + i);
210
    }
211

    
212
    for (; i < buf_size - 1; i += 4) {
213
        x = AV_RB32(buf + i);
214
        if (((x & ~(x + 0x01010101)) & 0x80808080)) {
215
            for (j = 0; j < 4; j++) {
216
                if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
217
                    size = find_headers_search_validate(fpc, search_start + i + j);
218
            }
219
        }
220
    }
221
    return size;
222
}
223

    
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static int find_new_headers(FLACParseContext *fpc, int search_start)
225
{
226
    FLACHeaderMarker *end;
227
    int search_end, size = 0, read_len, temp;
228
    uint8_t *buf;
229
    fpc->nb_headers_found = 0;
230

    
231
    /* Search for a new header of at most 16 bytes. */
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    search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
233
    read_len   = search_end - search_start + 1;
234
    buf        = flac_fifo_read(fpc, search_start, &read_len);
235
    size       = find_headers_search(fpc, buf, read_len, search_start);
236
    search_start += read_len - 1;
237

    
238
    /* If fifo end was hit do the wrap around. */
239
    if (search_start != search_end) {
240
        uint8_t wrap[2];
241

    
242
        wrap[0]  = buf[read_len - 1];
243
        read_len = search_end - search_start + 1;
244

    
245
        /* search_start + 1 is the post-wrap offset in the fifo. */
246
        buf      = flac_fifo_read(fpc, search_start + 1, &read_len);
247
        wrap[1]  = buf[0];
248

    
249
        if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
250
            temp = find_headers_search_validate(fpc, search_start);
251
            size = FFMAX(size, temp);
252
        }
253
        search_start++;
254

    
255
        /* Continue to do the last half of the wrap. */
256
        temp     = find_headers_search(fpc, buf, read_len, search_start);
257
        size     = FFMAX(size, temp);
258
        search_start += read_len - 1;
259
    }
260

    
261
    /* Return the size even if no new headers were found. */
262
    if (!size && fpc->headers)
263
        for (end = fpc->headers; end; end = end->next)
264
            size++;
265
    return size;
266
}
267

    
268
static int check_header_mismatch(FLACParseContext  *fpc,
269
                                 FLACHeaderMarker  *header,
270
                                 FLACHeaderMarker  *child,
271
                                 int                log_level_offset)
272
{
273
    FLACFrameInfo  *header_fi = &header->fi, *child_fi = &child->fi;
274
    int deduction = 0, deduction_expected = 0, i;
275
    if (child_fi->samplerate != header_fi->samplerate) {
276
        deduction += FLAC_HEADER_CHANGED_PENALTY;
277
        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
278
               "sample rate change detected in adjacent frames\n");
279
    }
280
    if (child_fi->bps != header_fi->bps) {
281
        deduction += FLAC_HEADER_CHANGED_PENALTY;
282
        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
283
               "bits per sample change detected in adjacent frames\n");
284
    }
285
    if (child_fi->is_var_size != header_fi->is_var_size) {
286
        /* Changing blocking strategy not allowed per the spec */
287
        deduction += FLAC_HEADER_BASE_SCORE;
288
        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
289
                   "blocking strategy change detected in adjacent frames\n");
290
    }
291
    if (child_fi->channels != header_fi->channels) {
292
        deduction += FLAC_HEADER_CHANGED_PENALTY;
293
        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
294
                   "number of channels change detected in adjacent frames\n");
295
    }
296
    /* Check sample and frame numbers. */
297
    if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
298
         != header_fi->blocksize) &&
299
        (child_fi->frame_or_sample_num
300
         != header_fi->frame_or_sample_num + 1)) {
301
        FLACHeaderMarker *curr;
302
        int expected_frame_num, expected_sample_num;
303
        /* If there are frames in the middle we expect this deduction,
304
           as they are probably valid and this one follows it */
305

    
306
        expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
307
        curr = header;
308
        while (curr != child) {
309
            /* Ignore frames that failed all crc checks */
310
            for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
311
                if (curr->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY) {
312
                    expected_frame_num++;
313
                    expected_sample_num += curr->fi.blocksize;
314
                    break;
315
                }
316
            }
317
            curr = curr->next;
318
        }
319

    
320
        if (expected_frame_num  == child_fi->frame_or_sample_num ||
321
            expected_sample_num == child_fi->frame_or_sample_num)
322
            deduction_expected = deduction ? 0 : 1;
323

    
324
        deduction += FLAC_HEADER_CHANGED_PENALTY;
325
        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
326
                   "sample/frame number mismatch in adjacent frames\n");
327
    }
328

    
329
    /* If we have suspicious headers, check the CRC between them */
330
    if (deduction && !deduction_expected) {
331
        FLACHeaderMarker *curr;
332
        int read_len;
333
        uint8_t *buf;
334
        uint32_t crc = 1;
335
        int inverted_test = 0;
336

    
337
        /* Since CRC is expensive only do it if we haven't yet.
338
           This assumes a CRC penalty is greater than all other check penalties */
339
        curr = header->next;
340
        for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
341
            curr = curr->next;
342

    
343
        if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY ||
344
            header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) {
345
            FLACHeaderMarker *start, *end;
346

    
347
            /* Although overlapping chains are scored, the crc should never
348
               have to be computed twice for a single byte. */
349
            start = header;
350
            end   = child;
351
            if (i > 0 &&
352
                header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
353
                while (start->next != child)
354
                    start = start->next;
355
                inverted_test = 1;
356
            } else if (i > 0 &&
357
                       header->next->link_penalty[i-1] >=
358
                       FLAC_HEADER_CRC_FAIL_PENALTY ) {
359
                end = header->next;
360
                inverted_test = 1;
361
            }
362

    
363
            read_len = end->offset - start->offset;
364
            buf      = flac_fifo_read(fpc, start->offset, &read_len);
365
            crc      = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
366
            read_len = (end->offset - start->offset) - read_len;
367

    
368
            if (read_len) {
369
                buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
370
                crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
371
            }
372
        }
373

    
374
        if (!crc ^ !inverted_test) {
375
            deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
376
            av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
377
                   "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
378
                   header->offset, header_fi->frame_or_sample_num,
379
                   child->offset, child_fi->frame_or_sample_num);
380
        }
381
    }
382
    return deduction;
383
}
384

    
385
/**
386
 * Score a header.
387
 *
388
 * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
389
 * If it has children, (subsequent frames of which the preceding CRC footer
390
 * validates against this one,) then take the maximum score of the children,
391
 * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
392
 * bps, sample rate, channels, but not decorrelation mode, or blocksize,
393
 * because it can change often.
394
 **/
395
static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header)
396
{
397
    FLACHeaderMarker *child;
398
    int dist = 0;
399
    int child_score;
400

    
401
    if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
402
        return header->max_score;
403

    
404
    header->max_score = FLAC_HEADER_BASE_SCORE;
405

    
406
    /* Check and compute the children's scores. */
407
    child = header->next;
408
    for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
409
        /* Look at the child's frame header info and penalize suspicious
410
           changes between the headers. */
411
        if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
412
            header->link_penalty[dist] = check_header_mismatch(fpc, header,
413
                                                               child, AV_LOG_DEBUG);
414
        }
415
        child_score = score_header(fpc, child) - header->link_penalty[dist];
416

    
417
        if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
418
            /* Keep the child because the frame scoring is dynamic. */
419
            header->best_child = child;
420
            header->max_score  = FLAC_HEADER_BASE_SCORE + child_score;
421
        }
422
        child = child->next;
423
    }
424

    
425
    return header->max_score;
426
}
427

    
428
static void score_sequences(FLACParseContext *fpc)
429
{
430
    FLACHeaderMarker *curr;
431
    int best_score = FLAC_HEADER_NOT_SCORED_YET;
432
    /* First pass to clear all old scores. */
433
    for (curr = fpc->headers; curr; curr = curr->next)
434
        curr->max_score = FLAC_HEADER_NOT_SCORED_YET;
435

    
436
    /* Do a second pass to score them all. */
437
    for (curr = fpc->headers; curr; curr = curr->next) {
438
        if (score_header(fpc, curr) > best_score) {
439
            fpc->best_header = curr;
440
            best_score       = curr->max_score;
441
        }
442
    }
443
}
444

    
445
static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
446
                           int *poutbuf_size)
447
{
448
    FLACHeaderMarker *header = fpc->best_header;
449
    FLACHeaderMarker *child  = header->best_child;
450
    if (!child) {
451
        *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
452
    } else {
453
        *poutbuf_size = child->offset - header->offset;
454

    
455
        /* If the child has suspicious changes, log them */
456
        check_header_mismatch(fpc, header, child, 0);
457
    }
458

    
459
    fpc->avctx->sample_rate = header->fi.samplerate;
460
    fpc->avctx->channels    = header->fi.channels;
461
    fpc->avctx->frame_size  = header->fi.blocksize;
462
    *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
463
                                        &fpc->wrap_buf,
464
                                        &fpc->wrap_buf_allocated_size);
465

    
466
    fpc->best_header_valid = 0;
467
    /* Return the negative overread index so the client can compute pos.
468
       This should be the amount overread to the beginning of the child */
469
    if (child)
470
        return child->offset - av_fifo_size(fpc->fifo_buf);
471
    return 0;
472
}
473

    
474
static int flac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
475
                      const uint8_t **poutbuf, int *poutbuf_size,
476
                      const uint8_t *buf, int buf_size)
477
{
478
    FLACParseContext *fpc = s->priv_data;
479
    FLACHeaderMarker *curr;
480
    int nb_headers;
481
    const uint8_t *read_end   = buf;
482
    const uint8_t *read_start = buf;
483

    
484
    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
485
        FLACFrameInfo fi;
486
        if (frame_header_is_valid(avctx, buf, &fi))
487
            avctx->frame_size = fi.blocksize;
488
        *poutbuf      = buf;
489
        *poutbuf_size = buf_size;
490
        return buf_size;
491
    }
492

    
493
    fpc->avctx = avctx;
494
    if (fpc->best_header_valid)
495
        return get_best_header(fpc, poutbuf, poutbuf_size);
496

    
497
    /* If a best_header was found last call remove it with the buffer data. */
498
    if (fpc->best_header && fpc->best_header->best_child) {
499
        FLACHeaderMarker *temp;
500
        FLACHeaderMarker *best_child = fpc->best_header->best_child;
501

    
502
        /* Remove headers in list until the end of the best_header. */
503
        for (curr = fpc->headers; curr != best_child; curr = temp) {
504
            if (curr != fpc->best_header) {
505
                av_log(avctx, AV_LOG_DEBUG,
506
                       "dropping low score %i frame header from offset %i to %i\n",
507
                       curr->max_score, curr->offset, curr->next->offset);
508
            }
509
            temp = curr->next;
510
            av_freep(&curr->link_penalty);
511
            av_free(curr);
512
            fpc->nb_headers_buffered--;
513
        }
514
        /* Release returned data from ring buffer. */
515
        av_fifo_drain(fpc->fifo_buf, best_child->offset);
516

    
517
        /* Fix the offset for the headers remaining to match the new buffer. */
518
        for (curr = best_child->next; curr; curr = curr->next)
519
            curr->offset -= best_child->offset;
520

    
521
        fpc->nb_headers_buffered--;
522
        best_child->offset = 0;
523
        fpc->headers       = best_child;
524
        if (fpc->nb_headers_buffered >= FLAC_MIN_HEADERS) {
525
            fpc->best_header = best_child;
526
            return get_best_header(fpc, poutbuf, poutbuf_size);
527
        }
528
        fpc->best_header   = NULL;
529
    } else if (fpc->best_header) {
530
        /* No end frame no need to delete the buffer; probably eof */
531
        FLACHeaderMarker *temp;
532

    
533
        for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
534
            temp = curr->next;
535
            av_freep(&curr->link_penalty);
536
            av_free(curr);
537
        }
538
        fpc->headers = fpc->best_header->next;
539
        av_freep(&fpc->best_header->link_penalty);
540
        av_freep(&fpc->best_header);
541
    }
542

    
543
    /* Find and score new headers. */
544
    while ((buf && read_end < buf + buf_size &&
545
            fpc->nb_headers_buffered < FLAC_MIN_HEADERS)
546
           || (!buf && !fpc->end_padded)) {
547
        int start_offset;
548

    
549
        /* Pad the end once if EOF, to check the final region for headers. */
550
        if (!buf) {
551
            fpc->end_padded      = 1;
552
            buf_size = MAX_FRAME_HEADER_SIZE;
553
            read_end = read_start + MAX_FRAME_HEADER_SIZE;
554
        } else {
555
            /* The maximum read size is the upper-bound of what the parser
556
               needs to have the required number of frames buffered */
557
            int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
558
            read_end       = read_end + FFMIN(buf + buf_size - read_end,
559
                                              nb_desired * FLAC_AVG_FRAME_SIZE);
560
        }
561

    
562
        /* Fill the buffer. */
563
        if (av_fifo_realloc2(fpc->fifo_buf,
564
                             (read_end - read_start) + av_fifo_size(fpc->fifo_buf)) < 0) {
565
            av_log(avctx, AV_LOG_ERROR,
566
                   "couldn't reallocate buffer of size %td\n",
567
                   (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
568
            goto handle_error;
569
        }
570

    
571
        if (buf) {
572
            av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
573
                                  read_end - read_start, NULL);
574
        } else {
575
            int8_t pad[MAX_FRAME_HEADER_SIZE];
576
            memset(pad, 0, sizeof(pad));
577
            av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
578
        }
579

    
580
        /* Tag headers and update sequences. */
581
        start_offset = av_fifo_size(fpc->fifo_buf) -
582
                       ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
583
        start_offset = FFMAX(0, start_offset);
584
        nb_headers   = find_new_headers(fpc, start_offset);
585

    
586
        if (nb_headers < 0) {
587
            av_log(avctx, AV_LOG_ERROR,
588
                   "find_new_headers couldn't allocate FLAC header\n");
589
            goto handle_error;
590
        }
591

    
592
        fpc->nb_headers_buffered = nb_headers;
593
        /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
594
        if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
595
            if (buf && read_end < buf + buf_size) {
596
                read_start = read_end;
597
                continue;
598
            } else {
599
                goto handle_error;
600
            }
601
        }
602

    
603
        /* If headers found, update the scores since we have longer chains. */
604
        if (fpc->end_padded || fpc->nb_headers_found)
605
            score_sequences(fpc);
606

    
607
        /* restore the state pre-padding */
608
        if (fpc->end_padded) {
609
            /* HACK: drain the tail of the fifo */
610
            fpc->fifo_buf->wptr -= MAX_FRAME_HEADER_SIZE;
611
            fpc->fifo_buf->wndx -= MAX_FRAME_HEADER_SIZE;
612
            if (fpc->fifo_buf->wptr < 0) {
613
                fpc->fifo_buf->wptr += fpc->fifo_buf->end -
614
                    fpc->fifo_buf->buffer;
615
            }
616
            buf_size = 0;
617
            read_start = read_end = NULL;
618
        }
619
    }
620

    
621
    curr = fpc->headers;
622
    for (curr = fpc->headers; curr; curr = curr->next)
623
        if (!fpc->best_header || curr->max_score > fpc->best_header->max_score)
624
            fpc->best_header = curr;
625

    
626
    if (fpc->best_header) {
627
        fpc->best_header_valid = 1;
628
        if (fpc->best_header->offset > 0) {
629
            /* Output a junk frame. */
630
            av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
631
                   fpc->best_header->offset);
632

    
633
            /* Set frame_size to 0. It is unknown or invalid in a junk frame. */
634
            avctx->frame_size = 0;
635
            *poutbuf_size     = fpc->best_header->offset;
636
            *poutbuf          = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
637
                                                    &fpc->wrap_buf,
638
                                                    &fpc->wrap_buf_allocated_size);
639
            return buf_size ? (read_end - buf) : (fpc->best_header->offset -
640
                                           av_fifo_size(fpc->fifo_buf));
641
        }
642
        if (!buf_size)
643
            return get_best_header(fpc, poutbuf, poutbuf_size);
644
    }
645

    
646
handle_error:
647
    *poutbuf      = NULL;
648
    *poutbuf_size = 0;
649
    return read_end - buf;
650
}
651

    
652
static int flac_parse_init(AVCodecParserContext *c)
653
{
654
    FLACParseContext *fpc = c->priv_data;
655
    /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
656
       it drains.  This is allocated early to avoid slow reallocation. */
657
    fpc->fifo_buf = av_fifo_alloc(FLAC_AVG_FRAME_SIZE * (FLAC_MIN_HEADERS + 3));
658
    return 0;
659
}
660

    
661
static void flac_parse_close(AVCodecParserContext *c)
662
{
663
    FLACParseContext *fpc = c->priv_data;
664
    FLACHeaderMarker *curr = fpc->headers, *temp;
665

    
666
    while (curr) {
667
        temp = curr->next;
668
        av_freep(&curr->link_penalty);
669
        av_free(curr);
670
        curr = temp;
671
    }
672
    av_fifo_free(fpc->fifo_buf);
673
    av_free(fpc->wrap_buf);
674
}
675

    
676
AVCodecParser ff_flac_parser = {
677
    { CODEC_ID_FLAC },
678
    sizeof(FLACParseContext),
679
    flac_parse_init,
680
    flac_parse,
681
    flac_parse_close,
682
};