Hello, Im facing a strange behaviour of kdenlive when rendering my video.
The rendering operation seems to end correctly but it doesn't: first of all it lasts only 50 seconds, for a video which is almost 20 minutes long.
The file is generated but the video stops after 30 seconds.
This is the output of the console:

$ kdenlive
QWidget::insertAction: Attempt to insert null action
QWidget::insertAction: Attempt to insert null action
[mp3 @ 0x7f317dd3bfa0] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7f317dd58560] max_analyze_duration 5000000 reached at 5015510
Truncating packet of size 1024 to 221
Truncating packet of size 1024 to 1
Truncating packet of size 1024 to 221
Truncating packet of size 1024 to 1
[mp3 @ 0x7f317e133200] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7f317e151f20] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7f317e170420] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7f317e15a520] max_analyze_duration 5000000 reached at 5015510
Truncating packet of size 1024 to 42
Truncating packet of size 1024 to 1
Truncating packet of size 1024 to 42
Truncating packet of size 1024 to 1
[mp3 @ 0x7f317e5dcd20] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7f317e5cb140] max_analyze_duration 5000000 reached at 5015510
Truncating packet of size 1024 to 481
Truncating packet of size 1024 to 1
Truncating packet of size 1024 to 481
Truncating packet of size 1024 to 1
kdenlive(4563) Render::checkMaxThreads: // TRACTOR PROBLEM
//STARTING RENDERING: true , false , "/usr/bin/melt" , "hdv_1080_50i" , "avformat" , "-" , "/tmp/kde-aladino/kdenlivecF4563.mlt" , "/home/aladino/nerdest/vblog_-_028/test.mpg" , () , ("f=mpeg", "acodec=mp2", "ab=384k", "ar=48000", "vcodec=mpeg2video", "minrate=0", "vb=12000k", "bf=2", "b_strategy=1", "trellis=1", "aspect=@16/9", "threads=1", "real_time=-1") , -1 , -1
Started render process: "/usr/bin/melt" "/tmp/kde-aladino/kdenlivecF4563.mlt -profile hdv_1080_50i -consumer avformat:/home/aladino/nerdest/vblog_-_028/test.mpg progress=1 f=mpeg acodec=mp2 ab=384k ar=48000 vcodec=mpeg2video minrate=0 vb=12000k bf=2 b_strategy=1 trellis=1 aspect=@16/9 threads=1 real_time=-1"
Rendering of "/home/aladino/nerdest/vblog_-_028/test.mpg" finished

In case I choose the 2 pass generation of the video file the program does complain that something went wrong.
This is the console output:

[-- SKIPPING INITIAL PART--]

//STARTING RENDERING: true , false , "/usr/bin/melt" , "hdv_1080_50i" , "avformat" , "-" , "/tmp/kde-aladino/kdenliveBC4681.mlt" , "/home/aladino/nerdest/vblog_-_028/test.mpg" , () , ("f=mpeg", "acodec=mp2", "ab=384k", "ar=48000", "vcodec=mpeg2video", "minrate=0", "vb=12000k", "bf=2", "b_strategy=1", "trellis=1", "aspect=@16/9", "pass=1", "threads=1", "real_time=-1") , -1 , -1
Started render process: "/usr/bin/melt" "/tmp/kde-aladino/kdenliveBC4681.mlt -profile hdv_1080_50i -consumer avformat:/home/aladino/nerdest/vblog_-_028/test.mpg progress=1 f=mpeg acodec=mp2 ab=384k ar=48000 vcodec=mpeg2video minrate=0 vb=12000k bf=2 b_strategy=1 trellis=1 aspect=@16/9 pass=1 threads=1 real_time=-1"
Rendering of "/home/aladino/nerdest/vblog_-_028/test.mpg" finished
Started render process: "/usr/bin/melt" "/tmp/kde-aladino/kdenliveBC4681.mlt -profile hdv_1080_50i -consumer avformat:/home/aladino/nerdest/vblog_-_028/test.mpg progress=1 f=mpeg acodec=mp2 ab=384k ar=48000 vcodec=mpeg2video minrate=0 vb=12000k bf=2 b_strategy=1 trellis=1 aspect=@16/9 pass=2 threads=1 real_time=-1"
"Rendering of /home/aladino/nerdest/vblog_-_028/test.mpg aborted, resulting video will probably be corrupted."

On the Error Log Box of the Rendering Window I can read:
Rendering of /home/aladino/nerdest/vblog_-_028/test.mpg crashed
[mp3 @ 0x7fa05f734d20] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa05f7512e0] max_analyze_duration 5000000 reached at 5015510
Truncating packet of size 1024 to 221
Truncating packet of size 1024 to 1
Truncating packet of size 1024 to 221
Truncating packet of size 1024 to 1
[mp3 @ 0x7fa05f82dc80] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa05f84c900] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa05f855540] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa05f866260] max_analyze_duration 5000000 reached at 5015510
Truncating packet of size 1024 to 42 Truncating packet of size 1024 to 1
Truncating packet of size 1024 to 42 Truncating packet of size 1024 to 1
[mp3 @ 0x7fa05f860560] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa05f863f80] max_analyze_duration 5000000 reached at 5015510
Truncating packet of size 1024 to 481
Truncating packet of size 1024 to 1
Truncating packet of size 1024 to 481
Truncating packet of size 1024 to 1
[mpeg2video @ 0x7fa03455ad40] warning: first frame is no keyframe
[mpeg2video @ 0x7fa03455ad40] warning: first frame is no keyframe
[swscaler @ 0x7fa034639bc0] Warning: data is not aligned! This can lead to a speedloss
[mpeg @ 0x7fa03c5be200] VBV buffer size not set, muxing may fail
[mpeg2video @ 0x7fa02e08fc00] warning: first frame is no keyframe
[mpeg2video @ 0x7fa02e08fc00] warning: first frame is no keyframe
Truncating packet of size 1024 to 221
Truncating packet of size 1024 to 1
Truncating packet of size 1024 to 221
Truncating packet of size 1024 to 1
[mp3 @ 0x7fa0161d36e0] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa016df8120] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa016369980] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa01b0dd800] max_analyze_duration 5000000 reached at 5015510
Truncating packet of size 1024 to 221
Truncating packet of size 1024 to 221
[mp3 @ 0x7fa015e8c640] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x7fa034007660] max_analyze_duration 5000000 reached at 5015510
melt: /build/buildd/ffmpeg-0.10.6/libavcodec/ratecontrol.c:698: ff_rate_estimate_qscale: Assertion `picture_numbernum_entries' failed.

This occurs if I choose MPEG-2 as video format but if I choose MPEG-4 the result is the same, the only differece is that I cannot play the resulting (corrupted) file.

I read on a thread on this forum that the problem could be due to a repository issue so I added the suggested repository:

$ sudo add-apt-repository ppa:jon-severinsson/ffmpeg && sudo apt-get update && sudo apt-get upgrade

But this did not solve my problem.

At the moment my configuration i the following:
$ kdenlive -version
Qt: 4.8.3
KDE Development Platform: 4.9.5
Kdenlive: 0.9.2

$ melt -version
melt 0.8.0
Copyright (C) 2002-2012 Ushodaya Enterprises Limited

This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

ffmpeg -version
ffmpeg version 0.10.6-6:0.10.6-0ubuntu0jon1
built on Nov 12 2012 12:53:40 with gcc 4.7.2
configuration: --arch=amd64 --enable-pthreads --enable-runtime-cpudetect --extra-version='6:0.10.6-0ubuntu0jon1' --libdir=/usr/lib/x86_64-linux-gnu --disable-stripping --prefix=/usr --enable-bzlib --enable-libdc1394 --enable-libfreetype --enable-frei0r --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-librtmp --enable-libopencv --enable-libopenjpeg --enable-libpulse --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-vaapi --enable-vdpau --enable-libvorbis --enable-libvpx --enable-zlib --enable-gpl --enable-postproc --enable-libcdio --enable-x11grab --enable-libx264 --shlibdir=/usr/lib/x86_64-linux-gnu --enable-shared --disable-static
libavutil 51. 35.100 / 51. 35.100
libavcodec 53. 61.100 / 53. 61.100
libavformat 53. 32.100 / 53. 32.100
libavdevice 53. 4.100 / 53. 4.100
libavfilter 2. 61.100 / 2. 61.100
libswscale 2. 1.100 / 2. 1.100
libswresample 0. 6.100 / 0. 6.100
libpostproc 52. 0.100 / 52. 0.100

I can't understand what is wrong. Maybe something related to melt or ffmpeg? Missing libraries or wrong version?
Please help me, and tell me if you need other info.
Thank you in advance.

I solved the problem following the instructions I found on this threat: http://www.kdenlive.org/forum/rendering-suddenly-goes-100-after-first-title-clip

The problem occurred when a title clips was met and executing kdenlive fixed the problem and the video was rendered correctly.
I'll check the other suggestions of the thread to see if I'll be able to use kdenlive as normal user.