[Libav-user] what is "fltp" for audio when using ffmpeg

Wed Jul 31 09:43:31 CEST 2013

Hi All,

I got the problem when I try to capture audio + video from USB web cam by
ffmepg.
the problem is audio can not play when I use VLC to play the stream that
ffserver output.
the question is :
I use ffmepg the encode audio to "wmav1" but, I can see the log that is
output by audio filter.
the audio format is "fltp".
What is "fltp"? Does anyone have idea?

the log is :
ffmpeg -loglevel debug -f video4linux2 -r 30 -s 640x480 -input_format h264
-i
/dev/video1 -f alsa -ar 48000 -ac 2 -i hw:0  -vcodec copy -acodec wmav1
http://l
ocalhost:8090/feed1.ffm
ffmpeg version 2.0 Copyright (c) 2000-2013 the FFmpeg developers
  built on Jul 31 2013 14:26:37 with gcc 4.4.5-1.5.5p4 (GCC)
  configuration: --enable-cross-compile --cross-prefix=sdk-linux-
--arch=mips --target-os=linux --disable
-doc --disable-htmlpages --disable-manpages --disable-podpages
--disable-txtpages --disable-mips32r2 --dis
able-ffplay --disable-postproc --disable-runtime-cpudetect
--disable-swscale-alpha --disable-mipsdspr1 --d
isable-mipsdspr2 --disable-mipsfpu --enable-small
--prefix=/ffmpeg-2.0/romfs --bindir=/ffmpeg-2.0/romfs --disable-bsfs
--disable-filters --enable-gpl --enab
le-libfaac --enable-nonfree --enable-libx264
--extra-cflags=-I/ShareLib_Install/bin/../include
--extra-libs='-L/ShareLib_Install/bin/../lib -lx264' --enable
-filter='aformat,aresample,copy,format,fps,framestep,resample' --disa
libavutil      52. 38.100 / 52. 38.
100
  libavcodec     55. 18.102 / 55. 18.102
  libavformat    55. 12.100 / 55. 12.100
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 79.101 /  3. 79.101
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
Splitting the commandline.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging
level) with argument 'debug'.
Reading option '-f' ... matched as option 'f' (force format) with argument
'video4linux2'.
Reading option '-r' ... matched as option 'r' (set frame rate (Hz value,
fraction or abbreviation)) with a
rgument '30'.
Reading option '-s' ... matched as option 's' (set frame size (WxH or
abbreviation)) with argument '640x48
0'.
Reading option '-input_format' ... matched as AVOption 'input_format' with
argument 'h264'.
Reading option '-i' ... matched as input file with argument '/dev/video1'.
Reading option '-f' ... matched as option 'f' (force format) with argument
'alsa'.
Reading option '-ar' ... matched as option 'ar' (set audio sampling rate
(in Hz)) with argument '48000'.
Reading option '-ac' ... matched as option 'ac' (set number of audio
channels) with argument '2'.
Reading option '-i' ... matched as input file with argument 'hw:0'.
Reading option '-vcodec' ... matched as option 'vcodec' (force video codec
('copy' to copy stream)) with a
rgument 'copy'.
Reading option '-acodec' ... matched as option 'acodec' (force audio codec
('copy' to copy stream)) with a
rgument 'wmav1'.
Reading option 'http://localhost:8090/feed1.ffm' ... matched as output file.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument debug.
Successfully parsed a group of options.
Parsing a group of options: input file /dev/video1.
Applying option f (force format) with argument video4linux2.
Applying option r (set frame rate (Hz value, fraction or abbreviation))
with argument 30.
Applying option s (set frame size (WxH or abbreviation)) with argument
640x480.
Successfully parsed a group of options.
Opening an input file: /dev/video1.
[video4linux2,v4l2 @ 0x71ed30] fd:3 capabilities:4000001
[video4linux2,v4l2 @ 0x71ed30] Current input_channel: 0, input_name: Camera
1
[video4linux2,v4l2 @ 0x71ed30] Setting time per frame to 1/30
[h264 @ 0x71f990] Frame num gap 9 7
[video4linux2,v4l2 @ 0x71ed30] All info found
Input #0, video4linux2,v4l2, from '/dev/video1':
  Duration: N/A, start: 147.060000, bitrate: N/A
    Stream #0:0, 8, 1/1000000: Video: h264, yuv420p, 640x480, 1/2000000, -5
kb/s, 30 fps, 30 tbr, 1000k tb
n, 2000k tbc
Successfully opened the file.
Parsing a group of options: input file hw:0.
Applying option f (force format) with argument alsa.
Applying option ar (set audio sampling rate (in Hz)) with argument 48000.
Applying option ac (set number of audio channels) with argument 2.
Successfully parsed a group of options.
Opening an input file: hw:0.
Guessed Channel Layout for  Input Stream #1.0 : stereo
Input #1, alsa, from 'hw:0':
  Duration: N/A, start: 1375284807.118875, bitrate: 1536 kb/s
    Stream #1:0, 1, 1/1000000: Audio: pcm_s16le, 48000 Hz, stereo, s16,
1536 kb/s
Successfully opened the file.
Parsing a group of options: output file http://localhost:8090/feed1.ffm.
Applying option vcodec (force video codec ('copy' to copy stream)) with
argument copy.
Applying option acodec (force audio codec ('copy' to copy stream)) with
argument wmav1.
Successfully parsed a group of options.
Opening an output file: http://localhost:8090/feed1.ffm.
[ffm @ 0x7f2ff0] Format ffm probed with size=2048 and score=101
[AVIOContext @ 0x7f7590] Statistics: 4096 bytes read, 0 seeks
Wed Jul 31 15:33:27 2013 127.0.0.1 - - [GET] "/feed1.ffm HTTP/1.1" 200 4175
Successfully opened the file.
detected 1 logical cores
[graph 0 input from stream 1:0 @ 0x7f3440] Setting 'time_base' to value
'1/48000'
[graph 0 input from stream 1:0 @ 0x7f3440] Setting 'sample_rate' to value
'48000'
[graph 0 input from stream 1:0 @ 0x7f3440] Setting 'sample_fmt' to value
's16'
[graph 0 input from stream 1:0 @ 0x7f3440] Setting 'channel_layout' to
value '0x3'
[graph 0 input from stream 1:0 @ 0x7f3440] tb:1/48000 samplefmt:s16
samplerate:48000 chlayout:0x3
[audio format for output stream 0:0 @ 0x79c700] Setting 'sample_fmts' to
value 'fltp'
[audio format for output stream 0:0 @ 0x79c700] Setting 'sample_rates' to
value '48000'
[audio format for output stream 0:0 @ 0x79c700] Setting 'channel_layouts'
to value '0x3'
[audio format for output stream 0:0 @ 0x79c700] auto-inserting filter
'auto-inserted resampler 0' between
the filter 'Parsed_anull_0' and the filter 'audio format for output stream
0:0'
[AVFilterGraph @ 0x812790] query_formats: 4 queried, 9 merged, 3 already
done, 0 delayed
[auto-inserted resampler 0 @ 0x811210] ch:2 chl:stereo fmt:s16 r:48000Hz ->
ch:2 chl:stereo fmt:fltp r:480
00Hz
Output #0, ffm, to 'http://localhost:8090/feed1.ffm':
  Metadata:
    creation_time   : now
    encoder         : Lavf55.12.100
    Stream #0:0, 0, 1/1000000: Audio: wmav1, 48000 Hz, stereo, fltp, 128
kb/s
    Stream #0:1, 0, 1/1000000: Video: h264, yuv420p, 640x480, 1/30, q=2-31,
-5 kb/s, 30 fps, 1000k tbn, 30
 tbc
Stream mapping:
  Stream #1:0 -> #0:0 (pcm_s16le -> wmav1)
  Stream #0:0 -> #0:1 (copy)
Press [q] to stop, [?] for help
[alsa @ 0x8174e0] ALSA buffer xrun.
    Last message repeated 1 times    Last message repeated 2 times    Last
message repeated 3 times
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