[Libva] [PATCH v3 intel-driver 3/9] decoder: h264: simplify and optimize reference frame store updates.
Zhao, Yakui
yakui.zhao at intel.com
Tue Jun 3 19:11:20 PDT 2014
On Tue, 2014-06-03 at 10:43 -0600, Gwenole Beauchesne wrote:
> Simplify and optimize the update process of the reference frame store.
> Use less iterations to look up existing objects. Use a cache to store
> the free'd slots.
>
> Prerequisite: the reference_objects[] array was previously arranged in
> a way that the element at index i is exactly the object_surface that
> corresponds to the VA surface identified by the VAPictureH264.picture_id
> located at index i in the ReferenceFrames[] array.
As a whole, this patch looks good to me. Based on the hardware
requirement, it will be better that one reference picture later used is
not assigned for the other purpose even when it is not used in current
reference frame list. In such case this patch does some optimization
about DPB, which can defer the usage of one picture later used that is
not in current reference frame.especially when: one picture is not used
during decoding frame X while it is used during decoding frame X + 1.
Although it still has no improvment for the following scenario, it still
is an improvement.
>One picture is not used during decoding frame X and X + 1 while it
is used during decoding frame X + 2.
Of course the perfect solution is that the upper layer can assure that
one picture later used is still added into the DPB of current frame
although it is not used in current reference list. Anyway, this patch is
still one improvement.
>
> Theory of operations:
>
> 1. Obsolete entries are removed first, i.e. entries in the internal DPB
> that no longer have a match in the supplied ReferenceFrames[] array.
> That obsolete entry index is stored in a local cache: free_slots[].
>
> 2. This cache is completed with entries considered as "invalid" or "not
> present", sequentially while traversing the frame store for obsolete
> entries. At the end of this removal process, the free_slots[] array
> represents all possible indices in there that could be re-used for
> new reference frames to track.
>
> 3. The list of ReferenceFrames[] objects is traversed for new entries
> that are not already in the frame store. If an entry needs to be
> added, it is placed at the index obtained from the next free_slots[]
> element. There is no need to traverse the frame store array again,
> the next available slot can be known from that free_slots[] cache.
>
> Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne at intel.com>
> ---
> src/i965_decoder_utils.c | 107 ++++++++++++++++++++--------------------------
> 1 file changed, 46 insertions(+), 61 deletions(-)
>
> diff --git a/src/i965_decoder_utils.c b/src/i965_decoder_utils.c
> index 2570be9..c686235 100644
> --- a/src/i965_decoder_utils.c
> +++ b/src/i965_decoder_utils.c
> @@ -418,88 +418,73 @@ gen6_send_avc_ref_idx_state(
> }
>
> void
> -intel_update_avc_frame_store_index(VADriverContextP ctx,
> - struct decode_state *decode_state,
> - VAPictureParameterBufferH264 *pic_param,
> - GenFrameStore frame_store[MAX_GEN_REFERENCE_FRAMES])
> +intel_update_avc_frame_store_index(
> + VADriverContextP ctx,
> + struct decode_state *decode_state,
> + VAPictureParameterBufferH264 *pic_param,
> + GenFrameStore frame_store[MAX_GEN_REFERENCE_FRAMES]
> +)
> {
> - int i, j;
> -
> - assert(MAX_GEN_REFERENCE_FRAMES == ARRAY_ELEMS(pic_param->ReferenceFrames));
> -
> - for (i = 0; i < MAX_GEN_REFERENCE_FRAMES; i++) {
> - int found = 0;
> -
> - if (frame_store[i].surface_id == VA_INVALID_ID ||
> - frame_store[i].obj_surface == NULL)
> + int free_slots[MAX_GEN_REFERENCE_FRAMES];
> + int i, j, n, num_free_slots;
> + bool found;
> +
It will be better to fill the free_slots through the following two loops
instead of one loop, which is to try to defer the usage of the reference
picture later used that is not used in current reference frame list.
a. check the invalid surface_id or NULL surface and then add it into
free_slots.
b. check whether one picture is used by the current reference frame
list. If not, add it into the free_slots.
> + /* Remove obsolete entries from the internal DPB */
> + for (i = 0, n = 0; i < MAX_GEN_REFERENCE_FRAMES; i++) {
> + GenFrameStore * const fs = &frame_store[i];
> + if (fs->surface_id == VA_INVALID_ID || !fs->obj_surface) {
> + free_slots[n++] = i;
> continue;
> + }
>
> - assert(frame_store[i].frame_store_id != -1);
> -
> - for (j = 0; j < MAX_GEN_REFERENCE_FRAMES; j++) {
> - VAPictureH264 *ref_pic = &pic_param->ReferenceFrames[j];
> - if (ref_pic->flags & VA_PICTURE_H264_INVALID)
> + // Find whether the current entry is still a valid reference frame
> + found = false;
> + for (j = 0; j < ARRAY_ELEMS(decode_state->reference_objects); j++) {
> + struct object_surface * const obj_surface =
> + decode_state->reference_objects[j];
> + if (!obj_surface)
> continue;
> -
> - if (frame_store[i].surface_id == ref_pic->picture_id) {
> - found = 1;
> + if ((found = obj_surface == fs->obj_surface))
> break;
> - }
> }
>
> - /* remove it from the internal DPB */
> + // ... or remove it
> if (!found) {
> - frame_store[i].surface_id = VA_INVALID_ID;
> - frame_store[i].frame_store_id = -1;
> - frame_store[i].obj_surface = NULL;
> + fs->surface_id = VA_INVALID_ID;
> + fs->obj_surface = NULL;
> + fs->frame_store_id = -1;
> + free_slots[n++] = i;
> }
> }
> + num_free_slots = n;
>
> - for (i = 0; i < MAX_GEN_REFERENCE_FRAMES; i++) {
> - VAPictureH264 *ref_pic = &pic_param->ReferenceFrames[i];
> - int found = 0;
> -
> - if (ref_pic->flags & VA_PICTURE_H264_INVALID ||
> - ref_pic->picture_id == VA_INVALID_SURFACE ||
> - decode_state->reference_objects[i] == NULL)
> + /* Append the new reference frames */
> + for (i = 0, n = 0; i < ARRAY_ELEMS(decode_state->reference_objects); i++) {
> + struct object_surface * const obj_surface =
> + decode_state->reference_objects[i];
> + if (!obj_surface)
> continue;
>
> + // Find whether the current frame is not already in our frame store
> + found = false;
> for (j = 0; j < MAX_GEN_REFERENCE_FRAMES; j++) {
> - if (frame_store[j].surface_id == ref_pic->picture_id) {
> - found = 1;
> + if ((found = frame_store[j].obj_surface == obj_surface))
> break;
> - }
> }
>
> - /* add the new reference frame into the internal DPB */
> + // ... or add it
> if (!found) {
> - int frame_idx;
> - int slot_found;
> - struct object_surface *obj_surface = decode_state->reference_objects[i];
> -
> - slot_found = 0;
> - frame_idx = -1;
> - /* Find a free frame store index */
> - for (j = 0; j < MAX_GEN_REFERENCE_FRAMES; j++) {
> - if (frame_store[j].surface_id == VA_INVALID_ID ||
> - frame_store[j].obj_surface == NULL) {
> - frame_idx = j;
> - slot_found = 1;
> - break;
> - }
> + if (n < num_free_slots) {
> + GenFrameStore * const fs = &frame_store[free_slots[n++]];
> + fs->surface_id = obj_surface->base.id;
> + fs->obj_surface = obj_surface;
> + fs->frame_store_id = fs - frame_store;
> + }
> + else {
> + WARN_ONCE("No free slot found for DPB reference list!!!\n");
> }
> -
> -
> - if (slot_found) {
> - frame_store[j].surface_id = ref_pic->picture_id;
> - frame_store[j].frame_store_id = frame_idx;
> - frame_store[j].obj_surface = obj_surface;
> - } else {
> - WARN_ONCE("Not free slot for DPB reference list!!!\n");
> - }
> }
> }
> -
> }
>
> void
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