memory leaks

[Suhwan]

Summary of the bug:
There are memory leaks
How to reproduce:

% ffmpeg_g -y -i $PoC -loglevel 0 -map 0 tmp.dnxhd

ffmpeg version N-95389-gdd01947397 Copyright (c) 2000-2019 the FFmpeg developers
built with clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
configuration: --cc=clang --cxx=clang++ --ld=clang --enable-debug

Here's Valgrind log

==11233== HEAP SUMMARY:
==11233==     in use at exit: 1,096 bytes in 2 blocks
==11233==   total heap usage: 4,677 allocs, 4,675 frees, 10,283,849 bytes allocated
==11233== 
==11233== 1,064 bytes in 1 blocks are definitely lost in loss record 2 of 2
==11233==    at 0x9D3CE76: memalign (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==11233==    by 0x9D3CF91: posix_memalign (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==11233==    by 0x590E87D: av_malloc (mem.c:87)
==11233==    by 0x2D4ED80: avcodec_alloc_context3 (options.c:158)
==11233==    by 0x215433C: ff_frame_thread_encoder_init (frame_thread_encoder.c:198)
==11233==    by 0x344D79F: avcodec_open2 (utils.c:740)
==11233==    by 0x4A67F1: init_output_stream (ffmpeg.c:3507)
==11233==    by 0x48C2DB: transcode_step (ffmpeg.c:4599)
==11233==    by 0x48C2DB: transcode (ffmpeg.c:4682)
==11233==    by 0x487D53: main (ffmpeg.c:4884)
==11233== 
==11233== LEAK SUMMARY:
==11233==    definitely lost: 1,064 bytes in 1 blocks
==11233==    indirectly lost: 0 bytes in 0 blocks
==11233==      possibly lost: 0 bytes in 0 blocks
==11233==    still reachable: 32 bytes in 1 blocks
==11233==         suppressed: 0 bytes in 0 blocks
==11233== Reachable blocks (those to which a pointer was found) are not shown.
==11233== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==11233== 
==11233== For counts of detected and suppressed errors, rerun with: -v
==11233== ERROR SUMMARY: 82534 errors from 137 contexts (suppressed: 0 from 0)

ASAN log.

=================================================================
==8850==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 1064 byte(s) in 1 object(s) allocated from:
    #0 0x4de9e8 in posix_memalign (ffmpeg_asan+0x4de9e8)
    #1 0x8593011 in av_malloc ffmpeg/libavutil/mem.c:87:9
    #2 0x463700a in avcodec_alloc_context3 ffmpeg/libavcodec/options.c:158:28
    #3 0x50f32f9 in avcodec_open2 ffmpeg/libavcodec/utils.c:740:15
    #4 0x61c29b in init_output_stream ffmpeg/fftools/ffmpeg.c:3507:20
    #5 0x5e509d in transcode_step ffmpeg/fftools/ffmpeg.c:4599:19
    #6 0x5e509d in transcode ffmpeg/fftools/ffmpeg.c:4682
    #7 0x5db65b in main ffmpeg/fftools/ffmpeg.c:4884:9
    #8 0x7f13edc0cb96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310

SUMMARY: AddressSanitizer: 1064 byte(s) leaked in 1 allocation(s).

Please confirm.
Thanks

[Suhwan]

poc

[Elon Musk]

Duplicate of #8281