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ba7675a2d9
libavformat closes and reopens the parser on every reposition
(ff_read_frame_flush()), so each seek hands vc1_parse() a zeroed
VC1Context: profile reads as simple, and max_coded_width and
max_coded_height as zero, until an in-stream sequence header happens to
pass.
An entry point BDU reaching the parser in that state is read at the wrong
bit offset, because hrd_full[] precedes coded_size_flag only when the
sequence header set hrd_param_flag, which a zeroed context cannot know.
The bit taken for coded_size_flag is then the first hrd_full[] bit, so an
entry point whose leaky bucket is below half full falls back to the zero
pair and ff_set_dimensions() fails:
[vc1] [IMGUTILS] Picture size 0x0 is invalid
[vc1] Failed to set dimensions 0 0
while one above half full takes a coded size out of the following
payload. The same zeroed context also sends an advanced profile frame
header through the simple/main reader, so pict_type, repeat_pict and
field_order are whatever falls out of it; libavformat writes the first
two into the packet key flag and the packet duration.
Read the extradata headers once per parser instance, through the walk the
decoder shares. A track whose frames carry no start codes is unaffected,
and so is one whose landing packets repeat the sequence header; linear
reads are byte identical either way.
320 lines
11 KiB
C
320 lines
11 KiB
C
/*
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* VC-1 and WMV3 parser
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* Copyright (c) 2006-2007 Konstantin Shishkov
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* Partly based on vc9.c (c) 2005 Anonymous, Alex Beregszaszi, Michael Niedermayer
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg 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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* FFmpeg 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 FFmpeg; 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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*/
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/**
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* @file
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* VC-1 and WMV3 parser
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*/
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#include "libavutil/attributes.h"
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#include "libavutil/avassert.h"
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#include "parser.h"
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#include "parser_internal.h"
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#include "vc1.h"
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#include "get_bits.h"
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#include "vc1dsp.h"
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/** The maximum number of bytes of a sequence, entry point or
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* frame header whose values we pay any attention to */
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#define UNESCAPED_THRESHOLD 37
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/** The maximum number of bytes of a sequence, entry point or
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* frame header which must be valid memory (because they are
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* used to update the bitstream cache in skip_bits() calls)
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*/
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#define UNESCAPED_LIMIT 144
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typedef enum {
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NO_MATCH,
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ONE_ZERO,
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TWO_ZEROS,
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ONE
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} VC1ParseSearchState;
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typedef struct VC1ParseContext {
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ParseContext pc;
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VC1Context v;
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uint8_t prev_start_code;
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uint8_t extradata_parsed;
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size_t bytes_to_skip;
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uint8_t unesc_buffer[UNESCAPED_LIMIT];
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size_t unesc_index;
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VC1ParseSearchState search_state;
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} VC1ParseContext;
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static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,
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const uint8_t *buf, int buf_size)
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{
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/* Parse the header we just finished unescaping */
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VC1ParseContext *vpc = s->priv_data;
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GetBitContext gb;
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int ret;
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vpc->v.s.avctx = avctx;
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ret = init_get_bits8(&gb, buf, buf_size);
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av_assert1(ret >= 0); // buf_size is bounded by UNESCAPED_THRESHOLD
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switch (vpc->prev_start_code) {
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case VC1_CODE_SEQHDR & 0xFF:
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ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
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break;
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case VC1_CODE_ENTRYPOINT & 0xFF:
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ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
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break;
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case VC1_CODE_FRAME & 0xFF:
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if(vpc->v.profile < PROFILE_ADVANCED)
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ret = ff_vc1_parse_frame_header (&vpc->v, &gb);
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else
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ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
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if (ret < 0)
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break;
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/* keep AV_PICTURE_TYPE_BI internal to VC1 */
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if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
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s->pict_type = AV_PICTURE_TYPE_B;
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else
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s->pict_type = vpc->v.s.pict_type;
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if (vpc->v.broadcast){
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// process pulldown flags
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s->repeat_pict = 1;
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// Pulldown flags are only valid when 'broadcast' has been set.
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if (vpc->v.rff){
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// repeat field
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s->repeat_pict = 2;
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}else if (vpc->v.rptfrm){
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// repeat frames
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s->repeat_pict = vpc->v.rptfrm * 2 + 1;
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}
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}else{
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s->repeat_pict = 0;
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}
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if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
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s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
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else
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s->field_order = AV_FIELD_PROGRESSIVE;
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break;
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}
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s->format = vpc->v.chromaformat == 1 ? AV_PIX_FMT_YUV420P
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: AV_PIX_FMT_NONE;
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if (avctx->width && avctx->height) {
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s->width = avctx->width;
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s->height = avctx->height;
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s->coded_width = FFALIGN(avctx->coded_width, 16);
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s->coded_height = FFALIGN(avctx->coded_height, 16);
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}
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}
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/**
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* Seed the parse context from extradata, the way the decoder does at init.
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*
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* libavformat closes and reopens the parser on every reposition
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* (ff_read_frame_flush()), so each seek starts from a zeroed VC1Context: profile
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* reads as simple, and max_coded_width/max_coded_height as zero, until an
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* in-stream sequence header happens to pass. An entry point reaching a context in
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* that state is read at the wrong bit offset, because whether hrd_full[] precedes
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* coded_size_flag is a property of the sequence header, and the size it then
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* falls back to is the zero pair.
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*
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* Unlike the decoder, a parser that learns nothing here still runs: it keeps
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* reading headers out of the stream as it did before.
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*/
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static void vc1_parse_extradata(AVCodecParserContext *s, AVCodecContext *avctx)
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{
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VC1ParseContext *vpc = s->priv_data;
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int seq_initialized, ep_initialized;
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if (!avctx->extradata || avctx->extradata_size < 16)
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return;
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vpc->v.s.avctx = avctx;
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ff_vc1_decode_extradata(avctx, &vpc->v, &seq_initialized, &ep_initialized);
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}
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static int vc1_parse(AVCodecParserContext *s,
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AVCodecContext *avctx,
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const uint8_t **poutbuf, int *poutbuf_size,
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const uint8_t *buf, int buf_size)
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{
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/* Here we do the searching for frame boundaries and headers at
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* the same time. Only a minimal amount at the start of each
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* header is unescaped. */
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VC1ParseContext *vpc = s->priv_data;
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int pic_found = vpc->pc.frame_start_found;
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uint8_t *unesc_buffer = vpc->unesc_buffer;
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size_t unesc_index = vpc->unesc_index;
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VC1ParseSearchState search_state = vpc->search_state;
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int start_code_found = 0;
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int next = END_NOT_FOUND;
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int i = vpc->bytes_to_skip;
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if (!vpc->extradata_parsed) {
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vpc->extradata_parsed = 1;
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vc1_parse_extradata(s, avctx);
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}
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if (pic_found && buf_size == 0) {
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/* EOF considered as end of frame */
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memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
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vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
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next = 0;
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}
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while (i < buf_size) {
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uint8_t b;
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start_code_found = 0;
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while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
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b = buf[i++];
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unesc_buffer[unesc_index++] = b;
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if (search_state <= ONE_ZERO)
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search_state = b ? NO_MATCH : search_state + 1;
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else if (search_state == TWO_ZEROS) {
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if (b == 1)
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search_state = ONE;
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else if (b > 1) {
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if (b == 3)
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unesc_index--; // swallow emulation prevention byte
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search_state = NO_MATCH;
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}
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}
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else { // search_state == ONE
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// Header unescaping terminates early due to detection of next start code
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search_state = NO_MATCH;
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start_code_found = 1;
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break;
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}
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}
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if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
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unesc_index >= UNESCAPED_THRESHOLD &&
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vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
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{
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// No need to keep scanning the rest of the buffer for
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// start codes if we know it contains a complete frame and
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// we've already unescaped all we need of the frame header
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vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
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unesc_index = 0;
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break;
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}
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if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
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while (i < buf_size) {
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if (search_state == NO_MATCH) {
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i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);
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if (i < buf_size) {
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search_state = ONE_ZERO;
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}
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i++;
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} else {
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b = buf[i++];
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if (search_state == ONE_ZERO)
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search_state = b ? NO_MATCH : TWO_ZEROS;
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else if (search_state == TWO_ZEROS) {
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if (b >= 1)
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search_state = b == 1 ? ONE : NO_MATCH;
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}
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else { // search_state == ONE
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search_state = NO_MATCH;
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start_code_found = 1;
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break;
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}
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}
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}
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}
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if (start_code_found) {
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vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
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vpc->prev_start_code = b;
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unesc_index = 0;
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if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
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if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
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pic_found = 1;
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}
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else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)
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&& b != (VC1_CODE_ENDOFSEQ & 0xFF)) {
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next = i - 4;
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pic_found = b == (VC1_CODE_FRAME & 0xFF);
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break;
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}
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}
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}
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}
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vpc->pc.frame_start_found = pic_found;
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vpc->unesc_index = unesc_index;
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vpc->search_state = search_state;
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if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
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next = buf_size;
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} else {
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if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
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vpc->bytes_to_skip = 0;
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*poutbuf = NULL;
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*poutbuf_size = 0;
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return buf_size;
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}
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}
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/* If we return with a valid pointer to a combined frame buffer
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* then on the next call then we'll have been unhelpfully rewound
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* by up to 4 bytes (depending upon whether the start code
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* overlapped the input buffer, and if so by how much). We don't
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* want this: it will either cause spurious second detections of
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* the start code we've already seen, or cause extra bytes to be
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* inserted at the start of the unescaped buffer. */
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vpc->bytes_to_skip = 4;
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if (next < 0 && next != END_NOT_FOUND)
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vpc->bytes_to_skip += next;
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*poutbuf = buf;
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*poutbuf_size = buf_size;
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return next;
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}
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static av_cold int vc1_parse_init(AVCodecParserContext *s)
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{
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VC1ParseContext *vpc = s->priv_data;
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/* Report no picture type until a frame header has actually been read.
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* av_parser_init() leaves pict_type at AV_PICTURE_TYPE_I, and libavformat
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* marks a packet a key frame from that default; a track whose frames carry
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* no start codes yields no header to this parser at all. */
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s->pict_type = AV_PICTURE_TYPE_NONE;
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vpc->v.s.slice_context_count = 1;
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vpc->v.first_pic_header_flag = 1;
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vpc->v.parse_only = 1;
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vpc->prev_start_code = 0;
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vpc->extradata_parsed = 0;
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vpc->bytes_to_skip = 0;
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vpc->unesc_index = 0;
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vpc->search_state = NO_MATCH;
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ff_vc1dsp_init(&vpc->v.vc1dsp); /* startcode_find_candidate */
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return 0;
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}
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const FFCodecParser ff_vc1_parser = {
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PARSER_CODEC_LIST(AV_CODEC_ID_VC1),
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.priv_data_size = sizeof(VC1ParseContext),
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.init = vc1_parse_init,
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.parse = vc1_parse,
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.close = ff_parse_close,
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};
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