[libav-bugs] [Bug 518] New: gray images when using -ss before -i for MPEG-1 video

bugzilla-daemon at aruru.libav.org bugzilla-daemon at aruru.libav.org
Fri May 17 01:51:21 CEST 2013


https://bugzilla.libav.org/show_bug.cgi?id=518

           Summary: gray images when using -ss before -i for MPEG-1 video
           Product: Libav
           Version: 9
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: libavcodec
        AssignedTo: bugzilla at libav.org
        ReportedBy: shaddy at chunkofwood.com


Created attachment 408
  --> https://bugzilla.libav.org/attachment.cgi?id=408
the gray thumbnail

This bug has already been filed and fixed for FFMPEG:
http://ffmpeg.org/trac/ffmpeg/ticket/67

I was attempting to generate an image from an MPEG-1 video, but all the images
are solid gray. This is related to using the -ss option before the input (-i).
If I move the -ss option after the -i, the thumbnail is fine.

avconv -i 'deer-fare.mpg' -ss 4.7908567 -v error -y -strict 1 -bt 1000000000 -f
image2 -vframes 1 'deer-fare.jpg'
szeineddine at shaddy-break:~/Desktop$ avprobe -show_format -show_streams
deer-fare.mpg 
avprobe version 9.1, Copyright (c) 2007-2013 the Libav developers
  built on Jan 10 2013 13:51:42 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
[mpeg @ 0x28a5860] max_analyze_duration reached
Input #0, mpeg, from 'deer-fare.mpg':
  Duration: 00:00:47.90, start: 1.000000, bitrate: 396 kb/s
    Stream #0.0[0x1e0]: Video: mpeg1video, yuv420p, 438x246 [PAR 1:1 DAR
73:41], 104857 kb/s, 25 fps, 90k tbn, 25 tbc
    Stream #0.1[0x1c0]: Audio: mp2, 44100 Hz, 2 channels, s16p, 128 kb/s
# avprobe output

[format]
filename=deer-fare.mpg
nb_streams=2
format_name=mpeg
format_long_name=MPEG-PS (MPEG-2 Program Stream)
start_time=1.000000
duration=47.908567
size=2371584.000000
bit_rate=396018.000000

[streams.stream.0]
index=0
codec_name=mpeg1video
codec_long_name=MPEG-1 video
codec_type=video
codec_time_base=1/25
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
width=438
height=246
has_b_frames=1
sample_aspect_ratio=1\:1
display_aspect_ratio=73\:41
pix_fmt=yuv420p
level=-99
id=480
avg_frame_rate=25/1
bit_rate=104857200.000000
time_base=1/90000
start_time=1.000000
duration=47.880000

[streams.stream.1]
index=1
codec_name=mp2
codec_long_name=MP2 (MPEG audio layer 2)
codec_type=audio
codec_time_base=1/44100
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
sample_rate=44100.000000
channels=2
bits_per_sample=0
id=448
avg_frame_rate=0/0
bit_rate=128000.000000
time_base=1/90000
start_time=1.000000
duration=47.908567


szeineddine at shaddy-break:~/Desktop$ valgrind avconv -ss 4.7908567 -i
'deer-fare.mpg' -v error -y -strict 1 -bt 1000000000 -f image2 -vframes 1
'deer-fare.jpg'
==7869== Memcheck, a memory error detector
==7869== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==7869== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==7869== Command: avconv -ss 4.7908567 -i deer-fare.mpg -v error -y -strict 1
-bt 1000000000 -f image2 -vframes 1 deer-fare.jpg
==7869== 
[mpeg1video @ 0x70bf780] warning: first frame is no keyframe
==7869== 
==7869== HEAP SUMMARY:
==7869==     in use at exit: 0 bytes in 0 blocks
==7869==   total heap usage: 2,485 allocs, 2,485 frees, 5,099,544 bytes
allocated
==7869== 
==7869== All heap blocks were freed -- no leaks are possible
==7869== 
==7869== For counts of detected and suppressed errors, rerun with: -v
==7869== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2)

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