| /* | 
 |  * Copyright (c) 2016, Alliance for Open Media. All rights reserved | 
 |  * | 
 |  * This source code is subject to the terms of the BSD 2 Clause License and | 
 |  * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License | 
 |  * was not distributed with this source code in the LICENSE file, you can | 
 |  * obtain it at www.aomedia.org/license/software. If the Alliance for Open | 
 |  * Media Patent License 1.0 was not distributed with this source code in the | 
 |  * PATENTS file, you can obtain it at www.aomedia.org/license/patent. | 
 |  */ | 
 |  | 
 | #include <assert.h> | 
 | #include <limits.h> | 
 | #include <stdio.h> | 
 |  | 
 | #include "./av1_rtcd.h" | 
 | #include "./aom_dsp_rtcd.h" | 
 | #include "./aom_scale_rtcd.h" | 
 |  | 
 | #include "aom_mem/aom_mem.h" | 
 | #include "aom_ports/system_state.h" | 
 | #include "aom_ports/aom_once.h" | 
 | #include "aom_ports/aom_timer.h" | 
 | #include "aom_scale/aom_scale.h" | 
 | #include "aom_util/aom_thread.h" | 
 |  | 
 | #include "av1/common/alloccommon.h" | 
 | #include "av1/common/av1_loopfilter.h" | 
 | #include "av1/common/onyxc_int.h" | 
 | #include "av1/common/quant_common.h" | 
 | #include "av1/common/reconinter.h" | 
 | #include "av1/common/reconintra.h" | 
 |  | 
 | #include "av1/decoder/decodeframe.h" | 
 | #include "av1/decoder/decoder.h" | 
 | #include "av1/decoder/detokenize.h" | 
 |  | 
 | #if CONFIG_OBU | 
 | #include "av1/decoder/obu.h" | 
 | #endif  // CONFIG_OBU | 
 |  | 
 | static void initialize_dec(void) { | 
 |   static volatile int init_done = 0; | 
 |  | 
 |   if (!init_done) { | 
 |     av1_rtcd(); | 
 |     aom_dsp_rtcd(); | 
 |     aom_scale_rtcd(); | 
 |     av1_init_intra_predictors(); | 
 |     av1_init_wedge_masks(); | 
 |     init_done = 1; | 
 |   } | 
 | } | 
 |  | 
 | static void av1_dec_setup_mi(AV1_COMMON *cm) { | 
 |   cm->mi = cm->mip + cm->mi_stride + 1; | 
 |   cm->mi_grid_visible = cm->mi_grid_base + cm->mi_stride + 1; | 
 |   memset(cm->mi_grid_base, 0, | 
 |          cm->mi_stride * (cm->mi_rows + 1) * sizeof(*cm->mi_grid_base)); | 
 |  | 
 |   memset(cm->boundary_info, 0, | 
 |          cm->boundary_info_alloc_size * sizeof(*cm->boundary_info)); | 
 | } | 
 |  | 
 | static int av1_dec_alloc_mi(AV1_COMMON *cm, int mi_size) { | 
 |   cm->mip = aom_calloc(mi_size, sizeof(*cm->mip)); | 
 |   if (!cm->mip) return 1; | 
 |   cm->mi_alloc_size = mi_size; | 
 |   cm->mi_grid_base = (MODE_INFO **)aom_calloc(mi_size, sizeof(MODE_INFO *)); | 
 |   if (!cm->mi_grid_base) return 1; | 
 |   return 0; | 
 | } | 
 |  | 
 | static void av1_dec_free_mi(AV1_COMMON *cm) { | 
 |   aom_free(cm->mip); | 
 |   cm->mip = NULL; | 
 |   aom_free(cm->mi_grid_base); | 
 |   cm->mi_grid_base = NULL; | 
 | } | 
 |  | 
 | AV1Decoder *av1_decoder_create(BufferPool *const pool) { | 
 |   AV1Decoder *volatile const pbi = aom_memalign(32, sizeof(*pbi)); | 
 |   AV1_COMMON *volatile const cm = pbi ? &pbi->common : NULL; | 
 |  | 
 |   if (!cm) return NULL; | 
 |  | 
 |   av1_zero(*pbi); | 
 |  | 
 |   if (setjmp(cm->error.jmp)) { | 
 |     cm->error.setjmp = 0; | 
 |     av1_decoder_remove(pbi); | 
 |     return NULL; | 
 |   } | 
 |  | 
 |   cm->error.setjmp = 1; | 
 |  | 
 |   CHECK_MEM_ERROR(cm, cm->fc, | 
 |                   (FRAME_CONTEXT *)aom_memalign(32, sizeof(*cm->fc))); | 
 |   CHECK_MEM_ERROR(cm, cm->frame_contexts, | 
 |                   (FRAME_CONTEXT *)aom_memalign( | 
 |                       32, FRAME_CONTEXTS * sizeof(*cm->frame_contexts))); | 
 |   memset(cm->fc, 0, sizeof(*cm->fc)); | 
 |   memset(cm->frame_contexts, 0, FRAME_CONTEXTS * sizeof(*cm->frame_contexts)); | 
 |  | 
 |   pbi->need_resync = 1; | 
 |   once(initialize_dec); | 
 |  | 
 |   // Initialize the references to not point to any frame buffers. | 
 |   memset(&cm->ref_frame_map, -1, sizeof(cm->ref_frame_map)); | 
 |   memset(&cm->next_ref_frame_map, -1, sizeof(cm->next_ref_frame_map)); | 
 |  | 
 |   cm->current_video_frame = 0; | 
 |   pbi->ready_for_new_data = 1; | 
 |   pbi->common.buffer_pool = pool; | 
 |  | 
 |   cm->bit_depth = AOM_BITS_8; | 
 |   cm->dequant_bit_depth = AOM_BITS_8; | 
 |  | 
 |   cm->alloc_mi = av1_dec_alloc_mi; | 
 |   cm->free_mi = av1_dec_free_mi; | 
 |   cm->setup_mi = av1_dec_setup_mi; | 
 |  | 
 |   av1_loop_filter_init(cm); | 
 |  | 
 | #if CONFIG_AOM_QM | 
 |   aom_qm_init(cm); | 
 | #endif | 
 | #if CONFIG_LOOP_RESTORATION | 
 |   av1_loop_restoration_precal(); | 
 | #endif  // CONFIG_LOOP_RESTORATION | 
 | #if CONFIG_ACCOUNTING | 
 |   pbi->acct_enabled = 1; | 
 |   aom_accounting_init(&pbi->accounting); | 
 | #endif | 
 |  | 
 |   cm->error.setjmp = 0; | 
 |  | 
 |   aom_get_worker_interface()->init(&pbi->lf_worker); | 
 |  | 
 |   return pbi; | 
 | } | 
 |  | 
 | void av1_decoder_remove(AV1Decoder *pbi) { | 
 |   int i; | 
 |  | 
 |   if (!pbi) return; | 
 |  | 
 |   aom_get_worker_interface()->end(&pbi->lf_worker); | 
 |   aom_free(pbi->lf_worker.data1); | 
 |   aom_free(pbi->tile_data); | 
 |   for (i = 0; i < pbi->num_tile_workers; ++i) { | 
 |     AVxWorker *const worker = &pbi->tile_workers[i]; | 
 |     aom_get_worker_interface()->end(worker); | 
 |   } | 
 |   aom_free(pbi->tile_worker_info); | 
 |   aom_free(pbi->tile_workers); | 
 |  | 
 |   if (pbi->num_tile_workers > 0) { | 
 |     av1_loop_filter_dealloc(&pbi->lf_row_sync); | 
 |   } | 
 |  | 
 | #if CONFIG_ACCOUNTING | 
 |   aom_accounting_clear(&pbi->accounting); | 
 | #endif | 
 |  | 
 |   aom_free(pbi); | 
 | } | 
 |  | 
 | static int equal_dimensions(const YV12_BUFFER_CONFIG *a, | 
 |                             const YV12_BUFFER_CONFIG *b) { | 
 |   return a->y_height == b->y_height && a->y_width == b->y_width && | 
 |          a->uv_height == b->uv_height && a->uv_width == b->uv_width; | 
 | } | 
 |  | 
 | aom_codec_err_t av1_copy_reference_dec(AV1Decoder *pbi, int idx, | 
 |                                        YV12_BUFFER_CONFIG *sd) { | 
 |   AV1_COMMON *cm = &pbi->common; | 
 |   const int num_planes = av1_num_planes(cm); | 
 |  | 
 |   const YV12_BUFFER_CONFIG *const cfg = get_ref_frame(cm, idx); | 
 |   if (cfg == NULL) { | 
 |     aom_internal_error(&cm->error, AOM_CODEC_ERROR, "No reference frame"); | 
 |     return AOM_CODEC_ERROR; | 
 |   } | 
 |   if (!equal_dimensions(cfg, sd)) | 
 |     aom_internal_error(&cm->error, AOM_CODEC_ERROR, | 
 |                        "Incorrect buffer dimensions"); | 
 |   else | 
 |     aom_yv12_copy_frame(cfg, sd, num_planes); | 
 |  | 
 |   return cm->error.error_code; | 
 | } | 
 |  | 
 | aom_codec_err_t av1_set_reference_dec(AV1_COMMON *cm, int idx, | 
 |                                       YV12_BUFFER_CONFIG *sd) { | 
 |   const int num_planes = av1_num_planes(cm); | 
 |   YV12_BUFFER_CONFIG *ref_buf = NULL; | 
 |  | 
 |   // Get the destination reference buffer. | 
 |   ref_buf = get_ref_frame(cm, idx); | 
 |  | 
 |   if (ref_buf == NULL) { | 
 |     aom_internal_error(&cm->error, AOM_CODEC_ERROR, "No reference frame"); | 
 |     return AOM_CODEC_ERROR; | 
 |   } | 
 |  | 
 |   if (!equal_dimensions(ref_buf, sd)) { | 
 |     aom_internal_error(&cm->error, AOM_CODEC_ERROR, | 
 |                        "Incorrect buffer dimensions"); | 
 |   } else { | 
 |     // Overwrite the reference frame buffer. | 
 |     aom_yv12_copy_frame(sd, ref_buf, num_planes); | 
 |   } | 
 |  | 
 |   return cm->error.error_code; | 
 | } | 
 |  | 
 | /* If any buffer updating is signaled it should be done here. */ | 
 | static void swap_frame_buffers(AV1Decoder *pbi) { | 
 |   int ref_index = 0, mask; | 
 |   AV1_COMMON *const cm = &pbi->common; | 
 |   BufferPool *const pool = cm->buffer_pool; | 
 |   RefCntBuffer *const frame_bufs = cm->buffer_pool->frame_bufs; | 
 |  | 
 |   lock_buffer_pool(pool); | 
 |   for (mask = pbi->refresh_frame_flags; mask; mask >>= 1) { | 
 |     const int old_idx = cm->ref_frame_map[ref_index]; | 
 |     // Current thread releases the holding of reference frame. | 
 |     decrease_ref_count(old_idx, frame_bufs, pool); | 
 |  | 
 |     // Release the reference frame holding in the reference map for the decoding | 
 |     // of the next frame. | 
 |     if (mask & 1) decrease_ref_count(old_idx, frame_bufs, pool); | 
 |     cm->ref_frame_map[ref_index] = cm->next_ref_frame_map[ref_index]; | 
 |     ++ref_index; | 
 |   } | 
 |  | 
 | // Current thread releases the holding of reference frame. | 
 | #if CONFIG_FWD_KF | 
 |   const int check_on_show_existing_frame = | 
 |       !cm->show_existing_frame || cm->reset_decoder_state; | 
 | #else | 
 |   const int check_on_show_existing_frame = !cm->show_existing_frame; | 
 | #endif  // CONFIG_FWD_KF | 
 |   for (; ref_index < REF_FRAMES && check_on_show_existing_frame; ++ref_index) { | 
 |     const int old_idx = cm->ref_frame_map[ref_index]; | 
 |     decrease_ref_count(old_idx, frame_bufs, pool); | 
 |     cm->ref_frame_map[ref_index] = cm->next_ref_frame_map[ref_index]; | 
 |   } | 
 |  | 
 |   unlock_buffer_pool(pool); | 
 |   pbi->hold_ref_buf = 0; | 
 |   cm->frame_to_show = get_frame_new_buffer(cm); | 
 |  | 
 |   // TODO(zoeliu): To fix the ref frame buffer update for the scenario of | 
 |   //               cm->frame_parellel_decode == 1 | 
 |   if (!cm->frame_parallel_decode || !cm->show_frame) { | 
 |     lock_buffer_pool(pool); | 
 |     --frame_bufs[cm->new_fb_idx].ref_count; | 
 |     unlock_buffer_pool(pool); | 
 |   } | 
 |  | 
 |   // Invalidate these references until the next frame starts. | 
 |   for (ref_index = 0; ref_index < INTER_REFS_PER_FRAME; ref_index++) { | 
 |     cm->frame_refs[ref_index].idx = INVALID_IDX; | 
 |     cm->frame_refs[ref_index].buf = NULL; | 
 |   } | 
 | } | 
 |  | 
 | int av1_receive_compressed_data(AV1Decoder *pbi, size_t size, | 
 |                                 const uint8_t **psource) { | 
 |   AV1_COMMON *volatile const cm = &pbi->common; | 
 |   volatile const int num_planes = av1_num_planes(cm); | 
 |   BufferPool *volatile const pool = cm->buffer_pool; | 
 |   RefCntBuffer *volatile const frame_bufs = cm->buffer_pool->frame_bufs; | 
 |   const uint8_t *source = *psource; | 
 |   cm->error.error_code = AOM_CODEC_OK; | 
 |  | 
 |   if (size == 0) { | 
 |     // This is used to signal that we are missing frames. | 
 |     // We do not know if the missing frame(s) was supposed to update | 
 |     // any of the reference buffers, but we act conservative and | 
 |     // mark only the last buffer as corrupted. | 
 |     // | 
 |     // TODO(jkoleszar): Error concealment is undefined and non-normative | 
 |     // at this point, but if it becomes so, [0] may not always be the correct | 
 |     // thing to do here. | 
 |     if (cm->frame_refs[0].idx > 0) { | 
 |       assert(cm->frame_refs[0].buf != NULL); | 
 |       cm->frame_refs[0].buf->corrupted = 1; | 
 |     } | 
 |   } | 
 |  | 
 |   pbi->ready_for_new_data = 0; | 
 |  | 
 |   // Find a free buffer for the new frame, releasing the reference previously | 
 |   // held. | 
 |  | 
 |   // Check if the previous frame was a frame without any references to it. | 
 |   // Release frame buffer if not decoding in frame parallel mode. | 
 |   if (!cm->frame_parallel_decode && cm->new_fb_idx >= 0 && | 
 |       frame_bufs[cm->new_fb_idx].ref_count == 0) | 
 |     pool->release_fb_cb(pool->cb_priv, | 
 |                         &frame_bufs[cm->new_fb_idx].raw_frame_buffer); | 
 |  | 
 |   // Find a free frame buffer. Return error if can not find any. | 
 |   cm->new_fb_idx = get_free_fb(cm); | 
 |   if (cm->new_fb_idx == INVALID_IDX) return AOM_CODEC_MEM_ERROR; | 
 |  | 
 |   // Assign a MV array to the frame buffer. | 
 |   cm->cur_frame = &pool->frame_bufs[cm->new_fb_idx]; | 
 |  | 
 |   pbi->hold_ref_buf = 0; | 
 |   if (cm->frame_parallel_decode) { | 
 |     AVxWorker *const worker = pbi->frame_worker_owner; | 
 |     av1_frameworker_lock_stats(worker); | 
 |     frame_bufs[cm->new_fb_idx].frame_worker_owner = worker; | 
 |     // Reset decoding progress. | 
 |     pbi->cur_buf = &frame_bufs[cm->new_fb_idx]; | 
 |     pbi->cur_buf->row = -1; | 
 |     pbi->cur_buf->col = -1; | 
 |     av1_frameworker_unlock_stats(worker); | 
 |   } else { | 
 |     pbi->cur_buf = &frame_bufs[cm->new_fb_idx]; | 
 |   } | 
 |  | 
 |   if (setjmp(cm->error.jmp)) { | 
 |     const AVxWorkerInterface *const winterface = aom_get_worker_interface(); | 
 |     int i; | 
 |  | 
 |     cm->error.setjmp = 0; | 
 |     pbi->ready_for_new_data = 1; | 
 |  | 
 |     // Synchronize all threads immediately as a subsequent decode call may | 
 |     // cause a resize invalidating some allocations. | 
 |     winterface->sync(&pbi->lf_worker); | 
 |     for (i = 0; i < pbi->num_tile_workers; ++i) { | 
 |       winterface->sync(&pbi->tile_workers[i]); | 
 |     } | 
 |  | 
 |     lock_buffer_pool(pool); | 
 |     // Release all the reference buffers if worker thread is holding them. | 
 |     if (pbi->hold_ref_buf == 1) { | 
 |       int ref_index = 0, mask; | 
 |       for (mask = pbi->refresh_frame_flags; mask; mask >>= 1) { | 
 |         const int old_idx = cm->ref_frame_map[ref_index]; | 
 |         // Current thread releases the holding of reference frame. | 
 |         decrease_ref_count(old_idx, frame_bufs, pool); | 
 |  | 
 |         // Release the reference frame holding in the reference map for the | 
 |         // decoding of the next frame. | 
 |         if (mask & 1) decrease_ref_count(old_idx, frame_bufs, pool); | 
 |         ++ref_index; | 
 |       } | 
 |  | 
 | // Current thread releases the holding of reference frame. | 
 | #if CONFIG_FWD_KF | 
 |       const int check_on_show_existing_frame = | 
 |           !cm->show_existing_frame || cm->reset_decoder_state; | 
 | #else | 
 |       const int check_on_show_existing_frame = !cm->show_existing_frame; | 
 | #endif  // CONFIG_FWD_KF | 
 |       for (; ref_index < REF_FRAMES && check_on_show_existing_frame; | 
 |            ++ref_index) { | 
 |         const int old_idx = cm->ref_frame_map[ref_index]; | 
 |         decrease_ref_count(old_idx, frame_bufs, pool); | 
 |       } | 
 |       pbi->hold_ref_buf = 0; | 
 |     } | 
 |     // Release current frame. | 
 |     decrease_ref_count(cm->new_fb_idx, frame_bufs, pool); | 
 |     unlock_buffer_pool(pool); | 
 |  | 
 |     aom_clear_system_state(); | 
 |     return -1; | 
 |   } | 
 |  | 
 |   cm->error.setjmp = 1; | 
 |  | 
 | #if !CONFIG_OBU | 
 |   av1_decode_frame_headers_and_setup(pbi, source, source + size, psource); | 
 |   if (!cm->show_existing_frame) { | 
 |     const uint8_t *data = source + pbi->uncomp_hdr_size; | 
 |     av1_decode_tg_tiles_and_wrapup(pbi, data, source + size, psource, 0, | 
 |                                    cm->tile_rows * cm->tile_cols - 1, 1); | 
 |   } | 
 | #else | 
 |   av1_decode_frame_from_obus(pbi, source, source + size, psource); | 
 | #endif | 
 |  | 
 |   if (cm->error.error_code != AOM_CODEC_OK) return 1; | 
 |  | 
 | #if TXCOEFF_TIMER | 
 |   cm->cum_txcoeff_timer += cm->txcoeff_timer; | 
 |   fprintf(stderr, | 
 |           "txb coeff block number: %d, frame time: %ld, cum time %ld in us\n", | 
 |           cm->txb_count, cm->txcoeff_timer, cm->cum_txcoeff_timer); | 
 |   cm->txcoeff_timer = 0; | 
 |   cm->txb_count = 0; | 
 | #endif | 
 |  | 
 |   swap_frame_buffers(pbi); | 
 |  | 
 | #if CONFIG_EXT_TILE | 
 |   // For now, we only extend the frame borders when the whole frame is decoded. | 
 |   // Later, if needed, extend the border for the decoded tile on the frame | 
 |   // border. | 
 |   if (pbi->dec_tile_row == -1 && pbi->dec_tile_col == -1) | 
 | #endif  // CONFIG_EXT_TILE | 
 |     // TODO(debargha): Fix encoder side mv range, so that we can use the | 
 |     // inner border extension. As of now use the larger extension. | 
 |     // aom_extend_frame_inner_borders(cm->frame_to_show, num_planes); | 
 |     aom_extend_frame_borders(cm->frame_to_show, num_planes); | 
 |  | 
 |   aom_clear_system_state(); | 
 |  | 
 |   if (!cm->show_existing_frame) { | 
 |     cm->last_show_frame = cm->show_frame; | 
 |  | 
 |     // NOTE: It is not supposed to ref to any frame not used as reference | 
 |     if (cm->is_reference_frame) cm->prev_frame = cm->cur_frame; | 
 |  | 
 |     if (cm->seg.enabled && !cm->frame_parallel_decode) | 
 | #if CONFIG_SEGMENT_PRED_LAST | 
 |       cm->last_frame_seg_map = cm->prev_frame->seg_map; | 
 | #else | 
 |       av1_swap_current_and_last_seg_map(cm); | 
 | #endif | 
 |   } | 
 |  | 
 |   // Update progress in frame parallel decode. | 
 |   if (cm->frame_parallel_decode) { | 
 |     // Need to lock the mutex here as another thread may | 
 |     // be accessing this buffer. | 
 |     AVxWorker *const worker = pbi->frame_worker_owner; | 
 |     FrameWorkerData *const frame_worker_data = worker->data1; | 
 |     av1_frameworker_lock_stats(worker); | 
 |  | 
 |     if (cm->show_frame) { | 
 |       cm->current_video_frame++; | 
 |     } | 
 |     frame_worker_data->frame_decoded = 1; | 
 |     frame_worker_data->frame_context_ready = 1; | 
 |     av1_frameworker_signal_stats(worker); | 
 |     av1_frameworker_unlock_stats(worker); | 
 |   } else { | 
 |     cm->last_width = cm->width; | 
 |     cm->last_height = cm->height; | 
 |     cm->last_tile_cols = cm->tile_cols; | 
 |     cm->last_tile_rows = cm->tile_rows; | 
 |     if (cm->show_frame) { | 
 |       cm->current_video_frame++; | 
 |     } | 
 |   } | 
 |  | 
 |   cm->error.setjmp = 0; | 
 |   return 0; | 
 | } | 
 |  | 
 | int av1_get_raw_frame(AV1Decoder *pbi, YV12_BUFFER_CONFIG *sd) { | 
 |   AV1_COMMON *const cm = &pbi->common; | 
 |   if (pbi->ready_for_new_data == 1) return -1; | 
 |  | 
 |   pbi->ready_for_new_data = 1; | 
 |  | 
 |   /* no raw frame to show!!! */ | 
 |   if (!cm->show_frame) return -1; | 
 |  | 
 |   *sd = *cm->frame_to_show; | 
 |   aom_clear_system_state(); | 
 |   return 0; | 
 | } | 
 |  | 
 | int av1_get_frame_to_show(AV1Decoder *pbi, YV12_BUFFER_CONFIG *frame) { | 
 |   AV1_COMMON *const cm = &pbi->common; | 
 |  | 
 |   if (!cm->show_frame || !cm->frame_to_show) return -1; | 
 |  | 
 |   *frame = *cm->frame_to_show; | 
 |   return 0; | 
 | } | 
 |  | 
 | aom_codec_err_t av1_parse_superframe_index(const uint8_t *data, size_t data_sz, | 
 |                                            uint32_t sizes[8], int *count, | 
 |                                            int *index_size) { | 
 |   // A chunk ending with a byte matching 0xc0 is an invalid chunk unless | 
 |   // it is a super frame index. If the last byte of real video compression | 
 |   // data is 0xc0 the encoder must add a 0 byte. If we have the marker but | 
 |   // not the associated matching marker byte at the front of the index we have | 
 |   // an invalid bitstream and need to return an error. | 
 |  | 
 |   uint8_t marker; | 
 |   size_t frame_sz_sum = 0; | 
 |  | 
 |   assert(data_sz); | 
 |   marker = data[0]; | 
 |   *count = 0; | 
 |  | 
 |   if ((marker & 0xe0) == 0xc0) { | 
 |     const uint32_t frames = (marker & 0x7) + 1; | 
 |     const uint32_t mag = ((marker >> 3) & 0x3) + 1; | 
 |     const size_t index_sz = 2 + mag * (frames - 1); | 
 |     *index_size = (int)index_sz; | 
 |  | 
 |     // This chunk is marked as having a superframe index but doesn't have | 
 |     // enough data for it, thus it's an invalid superframe index. | 
 |     if (data_sz < index_sz) return AOM_CODEC_CORRUPT_FRAME; | 
 |  | 
 |     { | 
 |       const uint8_t marker2 = data[index_sz - 1]; | 
 |  | 
 |       // This chunk is marked as having a superframe index but doesn't have | 
 |       // the matching marker byte at the front of the index therefore it's an | 
 |       // invalid chunk. | 
 |       if (marker != marker2) return AOM_CODEC_CORRUPT_FRAME; | 
 |     } | 
 |  | 
 |     { | 
 |       // Found a valid superframe index. | 
 |       uint32_t i, j; | 
 |       const uint8_t *x = &data[1]; | 
 |  | 
 |       for (i = 0; i < frames - 1; ++i) { | 
 |         uint32_t this_sz = 0; | 
 |  | 
 |         for (j = 0; j < mag; ++j) this_sz |= ((uint32_t)(*x++)) << (j * 8); | 
 |         this_sz += 1; | 
 |         sizes[i] = this_sz; | 
 |         frame_sz_sum += this_sz; | 
 |       } | 
 |       sizes[i] = (uint32_t)(data_sz - index_sz - frame_sz_sum); | 
 |       *count = frames; | 
 |     } | 
 |   } | 
 |   return AOM_CODEC_OK; | 
 | } |