tools/target_enc_fuzzer: A64MULTI encoder is very slow, check and adjust threshold

Fixes: Timeout
Fixes: 69097/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_A64MULTI_fuzzer-5062757287264256

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

tools/target_enc_fuzzer.c

@@ -78,6 +78,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     uint32_t it = 0;
     uint64_t nb_samples = 0;
     AVDictionary *opts = NULL;
+    uint64_t ec_pixels = 0;
 
     if (!c) {
 #define ENCODER_SYMBOL0(CODEC) ff_##CODEC##_encoder
@@ -93,6 +94,9 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
         return 0;
 
     maxpixels = maxpixels_per_frame * maxiteration;
+    switch (c->p.id) {
+    case AV_CODEC_ID_A64_MULTI:         maxpixels  /= 65536;  break;
+    }
 
     maxpixels_per_frame  = FFMIN(maxpixels_per_frame , maxpixels);
 
@@ -168,6 +172,10 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     frame->height = ctx->height;
 
     while (data < end && it < maxiteration) {
+        ec_pixels += (ctx->width + 32LL) * (ctx->height + 32LL);
+        if (ec_pixels > maxpixels)
+            goto maximums_reached;
+
         res = av_frame_get_buffer(frame, 0);
         if (res < 0)
             error("Failed av_frame_get_buffer");
@@ -192,7 +200,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
 
         av_packet_unref(avpkt);
     }
-
+maximums_reached:
     encode(ctx, NULL, avpkt);
     av_packet_unref(avpkt);