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• avfilter's anull says "Rematrix is needed between stereo and 0 channels but there is not enough information to do it"

  24 mai 2017, par kuanyui

  I’m trying to write a transcoder according to FFMpeg’s official example with ffmpeg 3.2.4 (official prebuild Win32), and try to transcode a video with stereo audio stream source (from avformat’s dshow).

  In the example code, which passes anull into avfilter_graph_parse_ptr() for audio stream, and "time_base=1/44100:sample_rate=44100:sample_fmt=s16:channels=2:channel_layout=0x3" is passed into avfilter_graph_create_filter(), occurs error in the following avfilter_graph_config() :

  [auto-inserted scaler 0 @ 32f77600] w:iw h:ih flags:'bilinear' interl:0
  
  [Parsed_null_0 @ 2e9d79a0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'in' and the filter 'Parsed_null_0'
  
  [swscaler @ 3331bfe0] deprecated pixel format used, make sure you did set range correctly
  
  [auto-inserted scaler 0 @ 32f77600] w:1920 h:1080 fmt:yuvj422p sar:1/1 -> w:1920 h:1080 fmt:yuv420p sar:1/1 flags:0x2
  
  [libmp3lame @ 2e90a360] Channel layout not specified
  
  [in @ 3866e8a0] tb:1/44100 samplefmt:s16 samplerate:44100 chlayout:0x3
  
  [Parsed_anull_0 @ 330e8820] auto-inserting filter 'auto-inserted resampler 0' between the filter 'in' and the filter 'Parsed_anull_0'
  
  [auto-inserted resampler 0 @ 330e8dc0] [SWR @ 3809b620] Rematrix is needed between stereo and 0 channels but there is not enough information to do it
  
  [auto-inserted resampler 0 @ 330e8dc0] Failed to configure output pad on auto-inserted resampler 0

  I’ve googled for days but didn’t find any clue for it. Doesn’t what anull do is only "Pass the audio source unchanged to the output", why libav want to resample stereo to 0 channel ? What’s going wrong ?

• FFMPEG hevc_nvenc "No NVENC capable devices found" with NVidia GTX950M

  13 mai 2017, par NaturalBornCamper

  I get the error "No NVENC capable devices found" when trying a simple encoding like this, even skipping audio to make sure it’s not an audio problem :

  ffmpeg.exe -i input.mp4 -c:v hevc_nvenc -an out.mp4

  I also tried with more details, like setting the pixel format, the preset, the rate-control, the format.

  On the documentation page there :
  https://trac.ffmpeg.org/wiki/HWAccelIntro
  it says that if we get this error we should check for the pixel format. The video has yuv420p here and even specifying the format results in the same error.

  i also checked the NVidia supported cards and it says GeForce, but no details about the models :
  https://developer.nvidia.com/video-encode-decode-gpu-support-matrix#Encoder

  I tried h264_nvenc and it works perfectly however, the problem is only with hevc_nvenc
  Has anyone encountered this problem ?

  Complete console output :

  [h264 @ 0000000002534560] Reinit context to 1280x544, pix_fmt: yuv420p
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 1
  
      compatible_brands: isom
  
      creation_time   : 2014-05-23T13:04:15.000000Z
  
    Duration: 01:54:03.95, start: 0.000000, bitrate: 3193 kb/s
  
      Stream #0:0(und): Video: h264 (High), 1 reference frame (avc1 / 0x31637661), yuv420p(left), 1280x544 [SAR 1:1 DAR 40:17], 2750 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
  
      Metadata:
  
        creation_time   : 2014-05-23T11:25:27.000000Z
  
      Stream #0:1(spa): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 439 kb/s (default)
  
      Metadata:
  
        creation_time   : 2014-05-23T12:56:43.000000Z
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> hevc (hevc_nvenc))
  
  Press [q] to stop, [?] for help
  
  [h264 @ 000000000260ea40] Reinit context to 1280x544, pix_fmt: yuv420p
  
  [graph 0 input from stream 0:0 @ 0000000003857ec0] w:1280 h:544 pixfmt:yuv420p tb:1/24000 fr:24000/1001 sar:1/1 sws_param:flags=2
  
  [hevc_nvenc @ 00000000038574e0] Loaded Nvenc version 8.0
  
  [hevc_nvenc @ 00000000038574e0] Nvenc initialized successfully
  
  [hevc_nvenc @ 00000000038574e0] 1 CUDA capable devices found
  
  [hevc_nvenc @ 00000000038574e0] [ GPU #0 - < GeForce GTX 950M > has Compute SM 5.0 ]
  
  [hevc_nvenc @ 00000000038574e0] Codec not supported
  
  [hevc_nvenc @ 00000000038574e0] No NVENC capable devices found
  
  [hevc_nvenc @ 00000000038574e0] Nvenc unloaded
  
  Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
  
  Conversion failed!

• cannot locate symbol "avpriv_pix_fmt_bps_avi"

  14 mars 2017, par S. Le Galloudec

  I’m developping an android application using ffmpeg. I’m trying to decode a rtsp stream, and i have a problem with a symbol.
  After i finally compiled ffmpeg with this tuto :
  https://github.com/WritingMinds/ffmpeg-android

  I used a code i found here : Receiving RTSP stream using FFMPEG library

  But i have a problem when i run my program. I got this error :

  java.lang.UnsatisfiedLinkError : dlopen failed : cannot locate symbol "avpriv_pix_fmt_bps_avi" referenced by "/data/app/com.example.local.test_ffmpeg-2/lib/arm/libnative-lib.so"...

  The thing is that i checked into my .a to see if i had the symbol so i did :

  nm libavcodec.a | grep avpriv_pix

  It returned :

  00000060 R avpriv_pix_fmt_bps_avi
  
  00000000 R avpriv_pix_fmt_bps_mov
  
           U avpriv_pix_fmt_bps_avi
  
           U avpriv_pix_fmt_bps_mov

  So it looks like i have the symbol, but the U after means undefined, so i’m really confused. I’m not sure if my compilation failed somewhere or if the problem comes from my program.

  I’m using ndk 14, if someone has some ideas, that would be great :)

  Best regards