[FFmpeg-devel] [PATCH 14/18] avcodec/hevcdec: Don't allocate redundant HEVCContexts

[Michael Niedermayer]

On Fri, Jul 01, 2022 at 12:29:45AM +0200, Andreas Rheinhardt wrote:
> The HEVC decoder has both HEVCContext and HEVCLocalContext
> structures. The latter is supposed to be the structure
> containing the per-slicethread state.
> 
> Yet up until now that is not how it is handled in practice:
> Each HEVCLocalContext has a unique HEVCContext allocated for it
> and each of these coincides except in exactly one field: The
> corresponding HEVCLocalContext. This makes it possible to pass
> the HEVCContext everywhere where logically a HEVCLocalContext
> should be used. And up until recently, this is how it has been done.
> 
> Yet the preceding patches changed this, making it possible
> to avoid allocating redundant HEVCContexts.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
>  libavcodec/hevcdec.c | 40 ++++++++++++++++------------------------
>  libavcodec/hevcdec.h |  2 --
>  2 files changed, 16 insertions(+), 26 deletions(-)
> 
> diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
> index 9d1241f293..048fcc76b4 100644
> --- a/libavcodec/hevcdec.c
> +++ b/libavcodec/hevcdec.c
> @@ -2548,13 +2548,12 @@ static int hls_decode_entry_wpp(AVCodecContext *avctxt, void *hevc_lclist,
>  {
>      HEVCLocalContext *lc = ((HEVCLocalContext**)hevc_lclist)[self_id];
>      const HEVCContext *const s = lc->parent;
> -    HEVCContext *s1  = avctxt->priv_data;
> -    int ctb_size    = 1<< s1->ps.sps->log2_ctb_size;
> +    int ctb_size    = 1 << s->ps.sps->log2_ctb_size;
>      int more_data   = 1;
>      int ctb_row = job;
> -    int ctb_addr_rs = s1->sh.slice_ctb_addr_rs + ctb_row * ((s1->ps.sps->width + ctb_size - 1) >> s1->ps.sps->log2_ctb_size);
> -    int ctb_addr_ts = s1->ps.pps->ctb_addr_rs_to_ts[ctb_addr_rs];
> -    int thread = ctb_row % s1->threads_number;
> +    int ctb_addr_rs = s->sh.slice_ctb_addr_rs + ctb_row * ((s->ps.sps->width + ctb_size - 1) >> s->ps.sps->log2_ctb_size);
> +    int ctb_addr_ts = s->ps.pps->ctb_addr_rs_to_ts[ctb_addr_rs];
> +    int thread = ctb_row % s->threads_number;
>      int ret;
>  
>      if(ctb_row) {
> @@ -2572,7 +2571,7 @@ static int hls_decode_entry_wpp(AVCodecContext *avctxt, void *hevc_lclist,
>  
>          ff_thread_await_progress2(s->avctx, ctb_row, thread, SHIFT_CTB_WPP);
>  
> -        if (atomic_load(&s1->wpp_err)) {
> +        if (atomic_load(&s->wpp_err)) {
>              ff_thread_report_progress2(s->avctx, ctb_row , thread, SHIFT_CTB_WPP);

the consts in "const HEVCContext *const " make clang version 6.0.0-1ubuntu2 unhappy
(this was building shared libs)


CC	libavcodec/hevcdec.o
src/libavcodec/hevcdec.c:2574:13: error: address argument to atomic operation must be a pointer to non-const _Atomic type ('const atomic_int *' (aka 'const _Atomic(int) *') invalid)
        if (atomic_load(&s->wpp_err)) {
            ^           ~~~~~~~~~~~
/usr/lib/llvm-6.0/lib/clang/6.0.0/include/stdatomic.h:134:29: note: expanded from macro 'atomic_load'
#define atomic_load(object) __c11_atomic_load(object, __ATOMIC_SEQ_CST)
                            ^                 ~~~~~~
1 error generated.
src/ffbuild/common.mak:81: recipe for target 'libavcodec/hevcdec.o' failed
make: *** [libavcodec/hevcdec.o] Error 1

thx

[...]
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