Check obu_type if single_picture_header_flag is 1 - #5322
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If single_picture_header_flag is equal to 1 in the sequence header OBU, frame_type is inferred to be KEY_FRAME. Therefore obu_type needs to be OBU_CLOSED_LOOP_KEY or OBU_OPEN_LOOP_KEY, otherwise frame_type and obu_type will be inconsistent with each other and things will go wrong. Fixes AOMediaCodec#5319.
wantehchang
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Aug 25, 2026
| if (obu_type == OBU_LEADING_SEF || obu_type == OBU_REGULAR_SEF) | ||
| return read_show_existing_frame(pbi, obu_type == OBU_REGULAR_SEF, rb); | ||
| if (obu_type == OBU_CLOSED_LOOP_KEY || obu_type == OBU_OPEN_LOOP_KEY) { | ||
| current_frame->frame_type = KEY_FRAME; |
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In the single_picture_header_flag=0 case, OBU_CLOSED_LOOP_KEY and OBU_OPEN_LOOP_KEY are mapped to KEY_FRAME.
| !cm->immediate_output_picture)) { | ||
| avm_internal_error(&cm->error, AVM_CODEC_CORRUPT_FRAME, | ||
| "Still pictures must be coded as shown keyframes"); | ||
| } |
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In the single_picture_header_flag=0 case, if still_picture is equal to 1, we require the OBU type be OBU_CLOSED_LOOP_KEY or OBU_OPEN_LOOP_KEY via the current_frame->frame_type != KEY_FRAME check. The check I added at line 8010 for the single_picture_header_flag=1 case matches this check.
However, I am not sure if we should allow OBU_OPEN_LOOP_KEY in a still-picture sequence. What do you think?
wantehchang
commented
Aug 25, 2026
| if (obu_type != OBU_CLOSED_LOOP_KEY && obu_type != OBU_OPEN_LOOP_KEY) { | ||
| avm_internal_error(&cm->error, AVM_CODEC_CORRUPT_FRAME, | ||
| "Still pictures must be coded as keyframes"); | ||
| } |
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Peter, Urvang: Do you know of a way to check if the still-picture sequence has more than one frame?
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If single_picture_header_flag is equal to 1 in the sequence header OBU, frame_type is inferred to be KEY_FRAME. Therefore obu_type needs to be OBU_CLOSED_LOOP_KEY or OBU_OPEN_LOOP_KEY, otherwise frame_type and obu_type will be inconsistent with each other and things will go wrong.
Fixes #5319.