Hello everyone,
I am experimenting unusual behaviour while transcoding live video via
libnvenc, and would like to ask if someone else had this problem or some
suggestion on what I am not doing right.
The situation: I want to transcode a live mpeg2 stream of ~16Mb/s to
h264, and got an nvidia gtx690 card for making this task. The incoming
stream is an mpeg ts from an antenna via hdhomerun ATSC tuner, and the
stream can be watched as mpeg2 just perfectly.
The problem: When I encode the stream as h264 mpeg ts segmented video
(or hls) **via libnvenc**, the stream can be played only if the player
(ffplay, etc) is started from the first segment, and the player will not
start when first segment gets outside the m3u list. The stream will play
from any starting point if the encoding is done with libx264.
The error given is that there is no key frame other than PPS0, what
makes no sense as the stream will be useless without keyframes - and it
plays just fine if started from the beginning. Trying to force key
frames or reduce the gop size makes no difference, up to now I found no
way to make the stream usable if not started from the beginning. Again,
this is only if transcoded via libnvenc.
I did upload transcoded files both via libnvenc and libx264 to
**http://downloads.znet.ca/ffmpeg-test/** , if someone is interested. It
is to be noted that any segment produced via libx264 will have keyframe
with all necessary information for being played alone, while only
segment 0 from the ones transcoded with libnvenc will have this
information. (NOTE: video produced with libx264 is of awful quality, but
can be played segment by segment; the one via libnvenc has very good
quality, but starts from segment 0 only)
------------------------------------
Transcoding:
ffmpeg -i udp://239.255.254.5:1234?overrun_nonfatal=1 -y -c:a copy -c:v
libnvenc -b:v 4M -profile:v high -preset ultrafast -bufsize 8M
-segment_format mpeg_ts ./m3u/TEST2/TS-nvenc.m3u8
The only difference when transcoding with libx264 is -c:v libx264.
The first segment trancoded via libnvenc and any segment transcoded via
libx264 will show following:
ggeorgiev@gtx690:/var/www/iptv/html$ ffprobe m3u/TEST2/TS-x2645.ts
ffprobe version 2.4.git Copyright (c) 2007-2014 the FFmpeg developers
built on Dec 21 2015 20:16:32 with gcc 4.9.2 (Debian 4.9.2-10)
configuration: --enable-libnvenc --enable-libfaac --enable-libfdk-aac
--enable-librtmp --enable-libx264 --enable-gpl --enable-nonfree
libavutil 54. 10.100 / 54. 10.100
libavcodec 56. 8.102 / 56. 8.102
libavformat 56. 9.101 / 56. 9.101
libavdevice 56. 1.100 / 56. 1.100
libavfilter 5. 1.106 / 5. 1.106
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, mpegts, from 'm3u/TEST2/TS-x2645.ts':
Duration: 00:00:08.37, start: 43.108333, bitrate: 4735 kb/s
Program 1
Metadata:
service_name : Service01
service_provider: FFmpeg
Stream #0:0[0x100]: Video: h264 (Constrained Baseline)
([27][0][0][0] / 0x001B), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 29.97
fps, 29.97 tbr, 90k tbn, 59.94 tbc
Stream #0:1[0x101]: Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz,
5.1(side), fltp, 384 kb/s
All segments, except the first one transcoded with libnvenc will show
following:
ggeorgiev@gtx690:/var/www/iptv/html$ ffprobe m3u/TEST2/TS-nvenc2.ts
ggeorgiev@gtx690:/var/www/iptv/html$ ffprobe m3u/TEST2/TS-nvenc2.ts
ffprobe version 2.4.git Copyright (c) 2007-2014 the FFmpeg developers
built on Dec 21 2015 20:16:32 with gcc 4.9.2 (Debian 4.9.2-10)
configuration: --enable-libnvenc --enable-libfaac --enable-libfdk-aac
--enable-librtmp --enable-libx264 --enable-gpl --enable-nonfree
libavutil 54. 10.100 / 54. 10.100
libavcodec 56. 8.102 / 56. 8.102
libavformat 56. 9.101 / 56. 9.101
libavdevice 56. 1.100 / 56. 1.100
libavfilter 5. 1.106 / 5. 1.106
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
[h264 @ 0x2aca460] non-existing PPS 0 referenced
Last message repeated 1 times
[h264 @ 0x2aca460] decode_slice_header error
[h264 @ 0x2aca460] no frame!
[h264 @ 0x2aca460] non-existing PPS 0 referenced
Last message repeated 1 times
[h264 @ 0x2aca460] decode_slice_header error
[h264 @ 0x2aca460] no frame!
[h264 @ 0x2aca460] non-existing PPS 0 referenced
Last message repeated 1 times
[h264 @ 0x2aca460] decode_slice_header error
......
...... --- exactly same lines repeating ----
......
[h264 @ 0x2aca460] non-existing PPS 0 referenced
Last message repeated 1 times
[h264 @ 0x2aca460] decode_slice_header error
[h264 @ 0x2aca460] no frame!
[mpegts @ 0x2ac64c0] decoding for stream 0 failed
[mpegts @ 0x2ac64c0] Could not find codec parameters for stream 0
(Video: h264 ([27][0][0][0] / 0x001B), none): unspecified size
Consider increasing the value for the 'analyzeduration' and 'probesize'
options
Input #0, mpegts, from 'm3u/TEST2/TS-nvenc2.ts':
Duration: 00:00:02.01, start: 5.404000, bitrate: 4867 kb/s
Program 1
Metadata:
service_name : Service01
service_provider: FFmpeg
Stream #0:0[0x100]: Video: h264 ([27][0][0][0] / 0x001B), none,
29.97 fps, 29.97 tbr, 90k tbn, 180k tbc
Stream #0:1[0x101]: Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz,
5.1(side), fltp, 384 kb/s
So, how it can be that key frames are invisible in the output produced
by libnvenc? And if so, how the stream can be played normally if there
are no key frames in it?
Any idea appreciated,
Thanks, george.
_______________________________________________
ffmpeg-user mailing list
[email protected]
http://ffmpeg.org/mailman/listinfo/ffmpeg-user
