[FFmpeg-devel,15/15] vp9_superframe: Avoid allocations and copies of packet structures

Up until now, the vp9_superframe bsf used distinct packets for input and
output. But at no point in the bsf are the input and output packets used
at the same time (except during a call to av_packet_move_ref()), so that
one can avoid using two packets if one switches to ff_bsf_get_packet_ref
at the same time. This also saves one malloc+free of an AVPacket
structure per filtered packet.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
---
 libavcodec/vp9_superframe_bsf.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

On 10/17/2019 5:29 AM, Andreas Rheinhardt wrote:
> Up until now, the vp9_superframe bsf used distinct packets for input and
> output. But at no point in the bsf are the input and output packets used
> at the same time (except during a call to av_packet_move_ref()), so that
> one can avoid using two packets if one switches to ff_bsf_get_packet_ref
> at the same time. This also saves one malloc+free of an AVPacket
> structure per filtered packet.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
> ---
>  libavcodec/vp9_superframe_bsf.c | 26 +++++++++++---------------
>  1 file changed, 11 insertions(+), 15 deletions(-)
> 
> diff --git a/libavcodec/vp9_superframe_bsf.c b/libavcodec/vp9_superframe_bsf.c
> index 23933d4136..b79911bb2c 100644
> --- a/libavcodec/vp9_superframe_bsf.c
> +++ b/libavcodec/vp9_superframe_bsf.c
> @@ -97,26 +97,25 @@ static int merge_superframe(AVPacket * const *in, int n_in, AVPacket *out)
>      return 0;
>  }
>  
> -static int vp9_superframe_filter(AVBSFContext *ctx, AVPacket *out)
> +static int vp9_superframe_filter(AVBSFContext *ctx, AVPacket *pkt)
>  {
>      GetBitContext gb;
>      VP9BSFContext *s = ctx->priv_data;
> -    AVPacket *in;
>      int res, invisible, profile, marker, uses_superframe_syntax = 0, n;
>  
> -    res = ff_bsf_get_packet(ctx, &in);
> +    res = ff_bsf_get_packet_ref(ctx, pkt);
>      if (res < 0)
>          return res;
>  
> -    marker = in->data[in->size - 1];
> +    marker = pkt->data[pkt->size - 1];
>      if ((marker & 0xe0) == 0xc0) {
>          int nbytes = 1 + ((marker >> 3) & 0x3);
>          int n_frames = 1 + (marker & 0x7), idx_sz = 2 + n_frames * nbytes;
>  
> -        uses_superframe_syntax = in->size >= idx_sz && in->data[in->size - idx_sz] == marker;
> +        uses_superframe_syntax = pkt->size >= idx_sz && pkt->data[pkt->size - idx_sz] == marker;
>      }
>  
> -    if ((res = init_get_bits8(&gb, in->data, in->size)) < 0)
> +    if ((res = init_get_bits8(&gb, pkt->data, pkt->size)) < 0)
>          goto done;
>  
>      get_bits(&gb, 2); // frame marker
> @@ -138,8 +137,7 @@ static int vp9_superframe_filter(AVBSFContext *ctx, AVPacket *out)
>          goto done;
>      } else if ((!invisible || uses_superframe_syntax) && !s->n_cache) {
>          // passthrough
> -        av_packet_move_ref(out, in);
> -        goto done;
> +        return 0;
>      } else if (s->n_cache + 1 >= MAX_CACHE) {
>          av_log(ctx, AV_LOG_ERROR,
>                 "Too many invisible frames\n");
> @@ -147,19 +145,18 @@ static int vp9_superframe_filter(AVBSFContext *ctx, AVPacket *out)
>          goto done;
>      }
>  
> -    av_packet_move_ref(s->cache[s->n_cache++], in);
> +    av_packet_move_ref(s->cache[s->n_cache++], pkt);
>  
>      if (invisible) {
> -        res = AVERROR(EAGAIN);
> -        goto done;
> +        return AVERROR(EAGAIN);
>      }
>      av_assert0(s->n_cache > 0);
>  
>      // build superframe
> -    if ((res = merge_superframe(s->cache, s->n_cache, out)) < 0)
> +    if ((res = merge_superframe(s->cache, s->n_cache, pkt)) < 0)
>          goto done;
>  
> -    res = av_packet_copy_props(out, s->cache[s->n_cache - 1]);
> +    res = av_packet_copy_props(pkt, s->cache[s->n_cache - 1]);
>      if (res < 0)
>          goto done;
>  
> @@ -169,8 +166,7 @@ static int vp9_superframe_filter(AVBSFContext *ctx, AVPacket *out)
>  
>  done:
>      if (res < 0)
> -        av_packet_unref(out);
> -    av_packet_free(&in);
> +        av_packet_unref(pkt);
>      return res;
>  }

Applied, thanks.