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• linker error in Android NDK r25c when cross-compiling FFmpeg

  5 août 2023, par Sai Chaithanya

  I am cross compiling FFmpeg for Android(aarch64) using Android NDK r25c on Linux x86_64 platform. The errors generated by the linker are because of enabling the LTO option.
  
On disabling the LTO options(--enable-lto optional config and -flto=thin cc-flag), there are no failures.

  


  FFmpeg config :

  


  ./configure --arch=aarch64 --target-os=android --enable-cross-compile --disable-everything \ 
 --disable-network --disable-autodetect --enable-small --disable-debug --disable-doc \ 
 --disable-manpages --disable-podpages --disable-txtpages --disable-htmlpages --disable-shared \
 --enable-static --enable-decoder='aac*,ac3*,opus,vorbis,mjpeg,mp3' \ 
 --enable-demuxer='mov,m4v,matroska,image2,mp3' --enable-protocol=file --enable-muxer='mp3,mp4,webm,null' \  
 --enable-libmp3lame --enable-encoder=libmp3lame --enable-filter=aresample --enable-logging \ 
 --enable-pthreads --enable-parser='vorbis,opus,vp8,vp9,mjpeg,h264,aac*,ac3*,mpegvideo,mpegaudio,mpeg4video' \
 --disable-ffprobe --disable-ffplay --prefix='$HOME/Downloads/custom_build' --enable-lto \
 --extra-cflags="-I$HOME/Downloads/custom_build/include -I$HOME/Downloads/android-ndk-r25c/toolchains/llvm/prebuilt/linux-x86_64/include -O3 -flto=thin" \
 --extra-ldflags="-L$HOME/Downloads/custom_build/lib -L$HOME/Downloads/android-ndk-r25c/toolchains/llvm/prebuilt/linux-x86_64/lib64" \
 --cc="aarch64-linux-android33-clang" --nm=llvm-nm --strip=llvm-strip


  


  Error :

  


  ld: error: undefined symbol: av_packet_alloc
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced 10 more times

ld: error: undefined symbol: av_usleep
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(main)
>>> referenced by ld-temp.o
>>>               lto.tmp:(retry_transfer_wrapper)

ld: error: undefined symbol: av_log
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced 745 more times

ld: error: undefined symbol: av_thread_message_queue_send
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced 1 more times

ld: error: undefined symbol: av_thread_message_queue_recv
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(main)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ffmpeg_cleanup)

ld: error: undefined symbol: av_rescale_q
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced 62 more times

ld: error: undefined symbol: av_packet_move_ref
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(submit_packet)
>>> referenced by ld-temp.o
>>>               lto.tmp:(pkt_move)
>>> referenced 3 more times

ld: error: undefined symbol: av_thread_message_queue_set_err_recv
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)

ld: error: undefined symbol: av_packet_free
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(input_thread)
>>> referenced by ld-temp.o
>>>               lto.tmp:(mux_check_init)
>>> referenced 13 more times

ld: error: undefined symbol: av_compare_ts
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_duration_update)
>>> referenced by ld-temp.o
>>>               lto.tmp:(finish_stream)
>>> referenced by ld-temp.o
>>>               lto.tmp:(finish_stream)
>>> referenced 10 more times

ld: error: undefined symbol: av_dict_set_int
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(of_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(mov_read_ftyp)
>>> referenced 1 more times

ld: error: undefined symbol: av_dict_get
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(configure_filtergraph)
>>> referenced by ld-temp.o
>>>               lto.tmp:(main)
>>> referenced 25 more times

ld: error: undefined symbol: av_opt_set_dict
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(init_output_stream_wrapper)
>>> referenced 4 more times

ld: error: undefined symbol: av_strdup
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced 29 more times

ld: error: undefined symbol: av_mallocz
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(graph_parse)
>>> referenced by ld-temp.o
>>>               lto.tmp:(graph_parse)
>>> referenced 62 more times

ld: error: undefined symbol: av_opt_set_defaults
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(avfilter_graph_alloc)
>>> referenced by ld-temp.o
>>>               lto.tmp:(avfilter_graph_alloc_filter)
>>> referenced 5 more times

ld: error: undefined symbol: av_fast_malloc
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)

ld: error: undefined symbol: av_free
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced 62 more times

ld: error: undefined symbol: av_freep
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced 205 more times

ld: error: undefined symbol: av_asprintf
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(ifile_open)
>>> referenced by ld-temp.o
>>>               lto.tmp:(describe_filter_link)
>>> referenced 3 more times

ld: error: too many errors emitted, stopping now (use -error-limit=0 to see all errors)
clang-14: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [Makefile:131: ffmpeg_g] Error 1


  


  I also compiled LAME encoder (version 3.100) with LTO options, and it worked just fine.
  
How to resolve the error ?

  


  **The libLTO.so file is present under lib64/ hence added that to the —extra-ldflags optional config.
  
**PATH env contains $HOME/Downloads/android-ndk-r25c/toolchains/llvm/prebuilt/linux-x86_64/bin

  


• FFMpeg fails to detect input stream when outputting to pipe's stdout

  27 septembre 2020, par La bla bla

  We have h264 frames as individual files, we read them to a python wrapper and piping them to ffmpeg.

  


  ffmpeg subprocess is launched using

  


      command = ["ffmpeg",
               "-hide_banner",
               "-vcodec", "h264",
               "-i", "pipe:0",
               "-video_size", "5120x3072",
               '-an', '-sn',  # we want to disable audio processing (there is no audio)
               '-pix_fmt', 'bgr24',
               "-vcodec", "rawvideo",
               '-f', 'image2pipe', '-']
    pipe = sp.Popen(command, stdin=sp.PIPE, stdout=sp.PIPE, bufsize=10 ** 8)


  


  Our goal is to use ffmpeg to convert the individual h264 frames into raw BGR data that we can manipulate using OpenCV.

  


  the files are read in a background thread and piped using

  


      ...
    for path in files:
        with open(path, "rb") as f:
            data = f.read()
            pipe.stdin.write(data)


  


  When we try to read the ffmpeg's output pipe using

  


      while True:
        # Capture frame-by-frame
        raw_image = pipe.stdout.read(width * height * 3)


  


  we get

  


  [h264 @ 0x1c31000] Could not find codec parameters for stream 0 (Video: h264, none): unspecified size
Consider increasing the value for the 'analyzeduration' and 'probesize' options
pipe:0: could not find codec parameters
Input #0, h264, from 'pipe:0':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: h264, none, 25 tbr, 1200k tbn, 50 tbc
Output #0, image2pipe, to 'pipe:':
Output file #0 does not contain any stream


  


  However, when I change the sp.Popen command to be

  


  
    f = open('ffmpeg_output.log', 'wt')
    pipe = sp.Popen(command, stdin=sp.PIPE, stdout=f, bufsize=10 ** 8) # Note: the stdout is not f


  


  we get the gibberish (i.e, binary data) in the ffmpeg_output.log file, and the console reads

  


  [h264 @ 0xf20000] Stream #0: not enough frames to estimate rate; consider increasing probesize
[h264 @ 0xf20000] decoding for stream 0 failed
Input #0, h264, from 'pipe:0':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: h264 (Baseline), yuv420p, 5120x3072, 25 fps, 25 tbr, 1200k tbn, 50 tbc
Output #0, image2pipe, to 'pipe:':
  Metadata:
    encoder         : Lavf56.40.101
    Stream #0:0: Video: rawvideo (BGR[24] / 0x18524742), bgr24, 5120x3072, q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
    Metadata:
      encoder         : Lavc56.60.100 rawvideo
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> rawvideo (native))
Invalid UE golomb code
    Last message repeated 89 times
Invalid UE golomb code
    Last message repeated 29 times
Invalid UE golomb code
    Last message repeated 29 times
Invalid UE golomb code
    Last message repeated 29 times
Invalid UE golomb code
    Last message repeated 29 times
Invalid UE golomb code
    Last message repeated 29 times
Invalid UE golomb code
    Last message repeated 29 times
Invalid UE golomb code
    Last message repeated 29 times
Invalid UE golomb code


  


  Why does ffmpeg cares if its stdout is a file or a pipe ?

  


• Trimming video without encoding

  14 octobre 2020, par Cristian Jorge A. Kusch

  I need to trim a video without encoding into sections that later i can put back together with the concat demuxer of ffmpeg.
I understand that to cut precisely without encoding it is necessary to cut at keyframes, i'm using this command to get the keyframes :

  


  ffprobe -loglevel error -select_streams v:0 -show_entries packet=pts_time,flags -of csv=print_section=0 -input | awk -F',' '/K/ {print $1}'


  


  and they also correspond to the times that Avidemux reports for the keyframes.
I'm using this command to trim the source :

  


  ffmpeg -ss 00:0:2.4607 -noaccurate_seek -avoid_negative_ts 1 -i input.mp4 -to 00:0:3.545 -c copy /content/losslessffmpeg.mp4


  


  But it always ends up with different durations. I would expect that if i cut between keyframe at time 2.460792 and keyframe at time 3.545208 i would get a video of lenght that is the difference between those two times, but it is never the case.
Any help ?
thanks