[Libav-user] First frame not keyframe

[Mark Kenna]

Hi Guys

I have an interesting issue where on trying to decode a mpeg1video file I
get:

[mpeg1video @ 01d16900] ignoring pic after 100
> [mpeg1video @ 01d16900] Missing picture start code
> [mpeg1video @ 01d16900] warning: first frame is no keyframe


After doing some research it appears that FFMpeg will drop the first frame
if it's deemed "broken, corrupt or not a keyframe", but it seems that the
first frame is present and looks perfectly valid when playing through
VLC/MPC. I have taken the following logs which indicate that the first
frame is indeed a non-keyframe. My questions is whether there is any way to
salvage the first frame (which is quite important for me) using FFMpeg?

Frame dump from FFProbe (I've cut down the info from the second frame)

[FRAME]
media_type=video
key_frame=0
pkt_pts=48000
pkt_pts_time=0.040000
pkt_dts=48000
pkt_dts_time=0.040000
pkt_duration=48000
pkt_duration_time=0.040000
pkt_pos=4096
width=320
height=240
pix_fmt=yuv420p
sample_aspect_ratio=1:1
pict_type=?
coded_picture_number=0
display_picture_number=0
interlaced_frame=0
top_field_first=0
repeat_pict=0
reference=3
[/FRAME]

[FRAME]
media_type=video
key_frame=0
pict_type=P
[/FRAME]

[FRAME]
key_frame=0
pict_type=P
[/FRAME]

[FRAME]
key_frame=0
pict_type=P
[/FRAME]

[FRAME]
key_frame=0
pict_type=P
[/FRAME]

[FRAME]
key_frame=1
pict_type=I
[/FRAME]


Packet dump from FFProbe

[PACKET]
codec_type=video
stream_index=0
pts=0
pts_time=0.000000
dts=0
dts_time=0.000000
duration=48000
duration_time=0.040000
size=4883
pos=N/A
flags=K
[/PACKET]

[PACKET]
codec_type=video
stream_index=0
pts=48000
pts_time=0.040000
dts=48000
dts_time=0.040000
duration=48000
duration_time=0.040000
size=28
pos=4096
flags=_
[/PACKET]

[PACKET]
codec_type=video
stream_index=0
pts=96000
pts_time=0.080000
dts=96000
dts_time=0.080000
duration=48000
duration_time=0.040000
size=28
pos=N/A
flags=_
[/PACKET]

Thanks guys,
Mark.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://ffmpeg.org/pipermail/libav-user/attachments/20121108/83c43fe0/attachment.html>