Fixes: Timeout (read mostly the same data repeatly)
Fixes: 52457/clusterfuzz-testcase-minimized-ffmpeg_dem_ALP_fuzzer-6610706313379840
Fixes: 53098/clusterfuzz-testcase-minimized-ffmpeg_dem_SOL_fuzzer-6481382981632000

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