Error while opening encoder for output stream #0:0 - ffmpeg

Question

I can't play a video using clipbucket after installation, getting conversion status as completed but while playing the video I get an message as "not available"
Conversion file
Checking File ....
File : /var/www/html/files/conversion_queue/14958856828d300.mp4
File Exists : Yes
Preparing file...
format : mov,mp4,m4a,3gp,3g2,mj2
duration : 62.09
size : 4480694
bitrate : 577316
video_width : 640
video_height : 360
video_wh_ratio : 1.7777777777778
video_codec : h264
video_rate : 23.976023976024
video_bitrate : 479302
video_color : N/A
audio_codec : aac
audio_bitrate : 95999
audio_rate : 44100
audio_channels : 2
path : /var/www/html/files/conversion_queue/14958856828d300.mp4
rotation : 0
======Converting Video=========
Starting : Thumbs Generation
=======Low Resolution Conversion=======
Sarting : Generating Low resolution video # 2017-05-27 17:18:11
Converting Video SD File
Command : /usr/local/bin/ffmpeg -i /var/www/html/files/conversion_queue/14958856828d300.mp4 -vcodec flv -acodec libmp3lame -s 640x360 -preset medium -f mp4 -b:v 512000 -minrate 512000 -maxrate 512000 -b:a 128000 -minrate 128000 -maxrate 128000 -r 25 -ar 22050 /var/www/html/files/videos/2017/05/27/14958856828d300-sd.mp4
ffmpeg output : ffmpeg version 2.6.8 Copyright (c) 2000-2016 the FFmpeg developers
built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-16)
configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic' --enable-bzlib --disable-crystalhd --enable-gnutls --enable-ladspa --enable-libass --enable-libdc1394 --enable-libfaac --enable-nonfree --disable-indev=jack --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-openal --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libx264 --enable-libx265 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-runtime-cpudetect
libavutil 54. 20.100 / 54. 20.100
libavcodec 56. 26.100 / 56. 26.100
libavformat 56. 25.101 / 56. 25.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 11.102 / 5. 11.102
libavresample 2. 1. 0 / 2. 1. 0
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/var/www/html/files/conversion_queue/14958856828d300.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: isommp42
creation_time : 2016-03-17 10:27:42
Duration: 00:01:02.09, start: 0.000000, bitrate: 577 kb/s
Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p(tv, bt709), 640x360 [SAR 1:1 DAR 16:9], 479 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 95 kb/s (default)
Metadata:
creation_time : 2016-03-17 10:27:42
handler_name : IsoMedia File Produced by Google, 5-11-2011
Codec AVOption preset (Set the encoding preset (cf. x264 --fullhelp)) specified for output file #0 (/var/www/html/files/videos/2017/05/27/14958856828d300-sd.mp4) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
[flv # 0x2506080] Either both buffer size and max rate or neither must be specified
Output #0, mp4, to '/var/www/html/files/videos/2017/05/27/14958856828d300-sd.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: isommp42
Stream #0:0(und): Video: flv1, none, q=2-31, 128 kb/s, SAR 1:1 DAR 0:0, 25 fps (default)
Metadata:
handler_name : VideoHandler
encoder : Lavc56.26.100 flv
Stream #0:1(eng): Audio: mp3, 0 channels, 128 kb/s (default)
Metadata:
creation_time : 2016-03-17 10:27:42
handler_name : IsoMedia File Produced by Google, 5-11-2011
encoder : Lavc56.26.100 libmp3lame
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> flv1 (flv))
Stream #0:1 -> #0:1 (aac (native) -> mp3 (libmp3lame))
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Sarting : MP4Box Conversion for SD
MP4Box Command : /usr/local/bin/MP4Box -inter 0.5 /var/www/html/files/videos/2017/05/27/14958856828d300-sd.mp4 -tmp /var/www/html/files/temp
output : Error opening file /var/www/html/files/videos/2017/05/27/14958856828d300-sd.mp4: IsoMedia File is truncated
Conversion Status : Successful # 2017-05-27 17:18:11
output_format : mov,mp4,m4a,3gp,3g2,mj2
output_duration : 62.09
output_size : 4480694
output_bitrate : 577316
output_video_width : 640
output_video_height : 360
output_video_wh_ratio : 1.7777777777778
output_video_codec : h264
output_video_rate : 23.976023976024
output_video_bitrate : 479302
output_video_color : N/A
output_audio_codec : aac
output_audio_bitrate : 95999
output_audio_rate : 44100
output_audio_channels : 2
output_path : /var/www/html/files/conversion_queue/14958856828d300.mp4
output_rotation : 0
Time Took : 9.2965 seconds
conversion_status : completed
**Error Messages**
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
output : Error opening file /var/www/html/files/videos/2017/05/27/14958856828d300-sd.mp4: IsoMedia File is truncated