#include "vc1.h"
#include "get_bits.h"
+/** The maximum number of bytes of a sequence, entry point or
+ * frame header whose values we pay any attention to */
+#define UNESCAPED_THRESHOLD 37
+
+/** The maximum number of bytes of a sequence, entry point or
+ * frame header which must be valid memory (because they are
+ * used to update the bitstream cache in skip_bits() calls)
+ */
+#define UNESCAPED_LIMIT 144
+
+typedef enum {
+ NO_MATCH,
+ ONE_ZERO,
+ TWO_ZEROS,
+ ONE
+} VC1ParseSearchState;
+
typedef struct {
ParseContext pc;
VC1Context v;
+ uint8_t prev_start_code;
+ size_t bytes_to_skip;
+ uint8_t unesc_buffer[UNESCAPED_LIMIT];
+ size_t unesc_index;
+ VC1ParseSearchState search_state;
} VC1ParseContext;
-static void vc1_extract_headers(AVCodecParserContext *s, AVCodecContext *avctx,
- const uint8_t *buf, int buf_size)
+static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,
+ const uint8_t *buf, int buf_size)
{
+ /* Parse the header we just finished unescaping */
VC1ParseContext *vpc = s->priv_data;
GetBitContext gb;
- const uint8_t *start, *end, *next;
- uint8_t *buf2 = av_mallocz(buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
-
+ int ret;
vpc->v.s.avctx = avctx;
vpc->v.parse_only = 1;
- vpc->v.first_pic_header_flag = 1;
- next = buf;
- s->repeat_pict = 0;
-
- for(start = buf, end = buf + buf_size; next < end; start = next){
- int buf2_size, size;
- int ret;
-
- next = find_next_marker(start + 4, end);
- size = next - start - 4;
- buf2_size = vc1_unescape_buffer(start + 4, size, buf2);
- init_get_bits(&gb, buf2, buf2_size * 8);
- if(size <= 0) continue;
- switch(AV_RB32(start)){
- case VC1_CODE_SEQHDR:
- ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
- break;
- case VC1_CODE_ENTRYPOINT:
- ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
- break;
- case VC1_CODE_FRAME:
- if(vpc->v.profile < PROFILE_ADVANCED)
- ret = ff_vc1_parse_frame_header (&vpc->v, &gb);
- else
- ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
-
- if (ret < 0)
- break;
-
- /* keep AV_PICTURE_TYPE_BI internal to VC1 */
- if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
- s->pict_type = AV_PICTURE_TYPE_B;
- else
- s->pict_type = vpc->v.s.pict_type;
-
- if (avctx->ticks_per_frame > 1){
- // process pulldown flags
- s->repeat_pict = 1;
- // Pulldown flags are only valid when 'broadcast' has been set.
- // So ticks_per_frame will be 2
- if (vpc->v.rff){
- // repeat field
- s->repeat_pict = 2;
- }else if (vpc->v.rptfrm){
- // repeat frames
- s->repeat_pict = vpc->v.rptfrm * 2 + 1;
- }
- }
-
- if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
- s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
- else
- s->field_order = AV_FIELD_PROGRESSIVE;
+ init_get_bits(&gb, buf, buf_size * 8);
+ switch (vpc->prev_start_code) {
+ case VC1_CODE_SEQHDR & 0xFF:
+ ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
+ break;
+ case VC1_CODE_ENTRYPOINT & 0xFF:
+ ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
+ break;
+ case VC1_CODE_FRAME & 0xFF:
+ if(vpc->v.profile < PROFILE_ADVANCED)
+ ret = ff_vc1_parse_frame_header (&vpc->v, &gb);
+ else
+ ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
+ if (ret < 0)
break;
- }
- }
- av_free(buf2);
-}
+ /* keep AV_PICTURE_TYPE_BI internal to VC1 */
+ if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
+ s->pict_type = AV_PICTURE_TYPE_B;
+ else
+ s->pict_type = vpc->v.s.pict_type;
-/**
- * Find the end of the current frame in the bitstream.
- * @return the position of the first byte of the next frame, or -1
- */
-static int vc1_find_frame_end(ParseContext *pc, const uint8_t *buf,
- int buf_size) {
- int pic_found, i;
- uint32_t state;
-
- pic_found= pc->frame_start_found;
- state= pc->state;
-
- i=0;
- if(!pic_found){
- for(i=0; i<buf_size; i++){
- state= (state<<8) | buf[i];
- if(state == VC1_CODE_FRAME || state == VC1_CODE_FIELD){
- i++;
- pic_found=1;
- break;
+ if (avctx->ticks_per_frame > 1){
+ // process pulldown flags
+ s->repeat_pict = 1;
+ // Pulldown flags are only valid when 'broadcast' has been set.
+ // So ticks_per_frame will be 2
+ if (vpc->v.rff){
+ // repeat field
+ s->repeat_pict = 2;
+ }else if (vpc->v.rptfrm){
+ // repeat frames
+ s->repeat_pict = vpc->v.rptfrm * 2 + 1;
}
+ }else{
+ s->repeat_pict = 0;
}
- }
- if(pic_found){
- /* EOF considered as end of frame */
- if (buf_size == 0)
- return 0;
- for(; i<buf_size; i++){
- state= (state<<8) | buf[i];
- if(IS_MARKER(state) && state != VC1_CODE_FIELD && state != VC1_CODE_SLICE){
- pc->frame_start_found=0;
- pc->state=-1;
- return i-3;
- }
- }
+ if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
+ s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
+ else
+ s->field_order = AV_FIELD_PROGRESSIVE;
+
+ break;
}
- pc->frame_start_found= pic_found;
- pc->state= state;
- return END_NOT_FOUND;
}
static int vc1_parse(AVCodecParserContext *s,
const uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size)
{
+ /* Here we do the searching for frame boundaries and headers at
+ * the same time. Only a minimal amount at the start of each
+ * header is unescaped. */
VC1ParseContext *vpc = s->priv_data;
- int next;
+ int pic_found = vpc->pc.frame_start_found;
+ uint8_t *unesc_buffer = vpc->unesc_buffer;
+ size_t unesc_index = vpc->unesc_index;
+ VC1ParseSearchState search_state = vpc->search_state;
+ int next = END_NOT_FOUND;
+ int i = vpc->bytes_to_skip;
+
+ if (pic_found && buf_size == 0) {
+ /* EOF considered as end of frame */
+ memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
+ vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
+ next = 0;
+ }
+ while (i < buf_size) {
+ int start_code_found = 0;
+ uint8_t b;
+ while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
+ b = buf[i++];
+ unesc_buffer[unesc_index++] = b;
+ if (search_state <= ONE_ZERO)
+ search_state = b ? NO_MATCH : search_state + 1;
+ else if (search_state == TWO_ZEROS) {
+ if (b == 1)
+ search_state = ONE;
+ else if (b > 1) {
+ if (b == 3)
+ unesc_index--; // swallow emulation prevention byte
+ search_state = NO_MATCH;
+ }
+ }
+ else { // search_state == ONE
+ // Header unescaping terminates early due to detection of next start code
+ search_state = NO_MATCH;
+ start_code_found = 1;
+ break;
+ }
+ }
+ if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
+ unesc_index >= UNESCAPED_THRESHOLD &&
+ vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
+ {
+ // No need to keep scanning the rest of the buffer for
+ // start codes if we know it contains a complete frame and
+ // we've already unescaped all we need of the frame header
+ vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
+ break;
+ }
+ if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
+ while (i < buf_size) {
+ if (search_state == NO_MATCH) {
+ i += vpc->v.vc1dsp.vc1_find_start_code_candidate(buf + i, buf_size - i);
+ if (i < buf_size) {
+ search_state = ONE_ZERO;
+ }
+ i++;
+ } else {
+ b = buf[i++];
+ if (search_state == ONE_ZERO)
+ search_state = b ? NO_MATCH : TWO_ZEROS;
+ else if (search_state == TWO_ZEROS) {
+ if (b >= 1)
+ search_state = b == 1 ? ONE : NO_MATCH;
+ }
+ else { // search_state == ONE
+ search_state = NO_MATCH;
+ start_code_found = 1;
+ break;
+ }
+ }
+ }
+ }
+ if (start_code_found) {
+ vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
+
+ vpc->prev_start_code = b;
+ unesc_index = 0;
+
+ if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
+ if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
+ pic_found = 1;
+ }
+ else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)) {
+ next = i - 4;
+ pic_found = b == (VC1_CODE_FRAME & 0xFF);
+ break;
+ }
+ }
+ }
+ }
- if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
- next= buf_size;
- }else{
- next= vc1_find_frame_end(&vpc->pc, buf, buf_size);
+ vpc->pc.frame_start_found = pic_found;
+ vpc->unesc_index = unesc_index;
+ vpc->search_state = search_state;
+ if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
+ next = buf_size;
+ } else {
if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
+ vpc->bytes_to_skip = 0;
*poutbuf = NULL;
*poutbuf_size = 0;
return buf_size;
}
}
- vc1_extract_headers(s, avctx, buf, buf_size);
+ vpc->v.first_pic_header_flag = 1;
+
+ /* If we return with a valid pointer to a combined frame buffer
+ * then on the next call then we'll have been unhelpfully rewound
+ * by up to 4 bytes (depending upon whether the start code
+ * overlapped the input buffer, and if so by how much). We don't
+ * want this: it will either cause spurious second detections of
+ * the start code we've already seen, or cause extra bytes to be
+ * inserted at the start of the unescaped buffer. */
+ vpc->bytes_to_skip = 4;
+ if (next < 0)
+ vpc->bytes_to_skip += next;
*poutbuf = buf;
*poutbuf_size = buf_size;
{
VC1ParseContext *vpc = s->priv_data;
vpc->v.s.slice_context_count = 1;
+ vpc->v.first_pic_header_flag = 1;
+ vpc->prev_start_code = 0;
+ vpc->bytes_to_skip = 0;
+ vpc->unesc_index = 0;
+ vpc->search_state = NO_MATCH;
return ff_vc1_init_common(&vpc->v);
}
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