[FFmpeg-user] RTMP WriteN error using NVENC while libx264 works fine

[Matthew Shapiro]

I am trying to run some transcoding tests to figure out how well ffmpeg
works on some GPU servers we have.

>From my desktop I am sending up an RTMP stream via OBS to a media server
system we have running.  I then started ffmpeg with arguments to pull that
feed from the media server and push it back to a different ingestion point
on that server.  So for example with libx264 I am invoking it with the
following:

ffmpeg -loglevel verbose -i "rtmp://server/live/matt-input live=1" -vcodec
libx264 -ar 44100 -f flv "rtmp://server/live/matt-test1"

This is meant as a bare bones basic test without doing any meaningful
conversion, and it works perfectly.  I"m able to subscribe to
rtmp://server/live/matt-test1 and see my vide out.

However, when I change libx264 to nvec:

ffmpeg -loglevel verbose -i "rtmp://server/live/matt-input live=1" -vcodec
nvenc -ar 44100 -f flv "rtmp://server/live/matt-test1"

After about 70-90 frames it gives me WriteN, RTMP send error 104 (136
bytes).  The metadata that ffmpeg sees from this video is:

Metadata:
  Server                NGINX RTMP (github.com/arut/nginx-rtmp-module)
  width                 1920.00
  height                1080.00
  displayWidth          1920.00
  displayHeight         1080.00
  duration              0.00
  framerate             30.00
  fps                   30.00
  videodatarate         0.00
  videocodecid          0.00
  audiodatarate         0.00
  audiocodecid          0.00
  profile
  level
Input #0, live_flv, from 'rtmp://server/live/matt-input live=1':
  Metadata:
    Server          : NGINX RTMP (github.com/arut/nginx-rtmp-module)
    displayWidth    : 1920
    displayHeight   : 1080
    fps             : 30
    profile         :
    level           :
  Duration: 00:00:00.00, start: 4.736000, bitrate: N/A
    Stream #0:0: Video: h264 (High), 3 reference frames, yuv420p(tv,
bt709/bt709/iec61966-2-1), 1920x1080 (1920x1088) [SAR 1:1 DAR 16:9], 30.30
fps, 30 tbr, 1k tbn, 60 tbc
    Stream #0:1: Audio: aac (LC), 48000 Hz, stereo, fltp


It appears that NVENC has some incompatibility when it comes to rtmp that
libx264 does not have.  It's also interesting to note that if I use ffmpeg
to encode the big buck bunny video and send it up to
rtmp://server/live/matt-input, then I am able to successfully use NVENC to
pull down the video and push it back up no problem.  For reference, the BBB
video is seen by FFMPEG as:

Metadata:
  Server                NGINX RTMP (github.com/arut/nginx-rtmp-module)
  width                 1920.00
  height                1080.00
  displayWidth          1920.00
  displayHeight         1080.00
  duration              0.00
  framerate             60.00
  fps                   60.00
  videodatarate         0.00
  videocodecid          7.00
  audiodatarate         125.00
  audiocodecid          1.00
  profile
  level
Input #0, live_flv, from 'rtmp://server/live/matt-input live=1':
  Metadata:
    Server          : NGINX RTMP (github.com/arut/nginx-rtmp-module)
    displayWidth    : 1920
    displayHeight   : 1080
    fps             : 60
    profile         :
    level           :
  Duration: 00:00:00.00, start: 1.950000, bitrate: N/A
    Stream #0:0: Video: h264 (High), yuv420p(tv), 1920x1080 [SAR 1:1 DAR
16:9], 62.50 fps, 60 tbr, 1k tbn, 120 tbc
    Stream #0:1: Audio: adpcm_swf, 44100 Hz, stereo, s16, 352 kb/s

Also, if needed I compiled FFMPEG using the instructions from
http://developer.download.nvidia.com/compute/redist/ffmpeg/1511-patch/FFMPEG-with-NVIDIA-Acceleration-on-Ubuntu_UG_v01.pdf,
and the beginning of the ffmpeg output looks like:

# ffmpeg -i "rtmp://server/live/matt-input live=1" -vcodec nvenc -ar 44100
-f flv "rtmp://server/live/matt-test1"
ffmpeg version N-76538-gb83c849 Copyright (c) 2000-2015 the FFmpeg
developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  configuration: --enable-nonfree --enable-nvenc --enable-nvresize
--extra-cflags=-I../cudautils --extra-ldflags=-L../cudautils --enable-gpl
--enable-libx264 --enable-librtmp
  libavutil      55.  5.100 / 55.  5.100
  libavcodec     57. 15.100 / 57. 15.100
  libavformat    57. 14.100 / 57. 14.100
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 15.100 /  6. 15.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100


I have tried changing my OBS settings one at a time (both multi-platform
and non-multiplatform versions) to no avail.  Pulling from other streams
seems to cause the same thing to happen, and the only stream I've been able
to pull, transcode, then re-push via RTMP (via NVENC) seems to be one that
originates straight from FFMPEG

Does anyone have any suggestions on what might be wrong?  Is there
something on my end that is causing rtmp to fail or is it a bug in the
NVENC encoder?