Original mail and my own followup on ffmpeg-user earlier today:
I have a device sending out a MJPEG/RTP stream on a low quality setting.
Decoding and displaying the video with libavformat results in a washed
out, low contrast, greyish image. Playing the same stream with VLC results
in proper color representation.
Screenshots for comparison:
http://zevv.nl/div/libav/shot-ffplay.jpghttp://zevv.nl/div/libav/shot-vlc.jpg
A pcap capture of a few seconds of video and SDP file for playing the
stream are available at
http://zevv.nl/div/libav/mjpeg.pcaphttp://zevv.nl/div/libav/mjpeg.sdp
I believe the problem might be in the calculation of the quantization
tables in the function create_default_qtables(), the attached patch
solves the issue for me.
The problem is that the argument 'q' is of the type uint8_t. According to the
JPEG standard, if 1 <= q <= 50, the scale factor 'S' should be 5000 / Q.
Because the create_default_qtables() reuses the variable 'q' to store the
result of this calculation, for small values of q < 19, q wil subsequently
overflow and give wrong results in the calculated quantization tables. The
patch below uses a new variable 'S' (same name as in RFC2435) with the proper
range to store the result of the division.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
All tests were in the main method which produces a long main. Now, each test
is in his own method.
I think this produces a more clear code and follows more with the main
priority of FFmpeg "simplicity and small code size"
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
No new reference samples are needed for this as the file already exists
for testing the bitstream filter
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
No idea why in commit 01ecb7172b the
checks were removed; this can lead to NULL pointer dereferences. This
effectively reverts that portion of the commit.
Reviewed-by: Benoit Fouet <benoit.fouet@free.fr>
Reviewed-by: Rostislav Pehlivanov <atomnuker@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanag@gmail.com>
The idea is to use ffmath.h for internal implementations of math functions.
Currently, it is used for variants of libm functions, but is by no means
limited to such things.
Note that this is not exported; use lavu/mathematics for such purposes.
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanag@gmail.com>
- Check if av_display_rotation_get() gets the correct degrees
- Check if av_display_rotation_set() sets the correct matrix
- Check if av_display_matrix_flip() changes correct the matrix
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
Until now, for formats which were in the spec but not in the encoder's
list of supported formats required the -strict -1 flag. This enables
support for all video formats which are specified, all the way from
QSIF525 to 8K.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
Adding early support for a subset of the proposed colour elements
according to the latest version of spec:
https://mailarchive.ietf.org/arch/search/?email_list=cellar&gbt=1&index=hIKLhMdgTMTEwUTeA4ct38h0tmE
Like matroskadec, I've left out elements for pix_fmt related things
as there still seems to be some discussion around these.
The new elements are exposed under strict experimental mode.
Signed-off-by: Neil Birkbeck <neil.birkbeck@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
dv_frame_offset() is static and called only from dv_read_seek(), where
c->sys->frame_size is already used.
This simplifies the incoming codecpar merge where
avctx->{coded_width,coded_height,time_base} are not accessible anymore.
Michael Niedermayer
Dan Dennedy
Carl Eugen Hoyos
Martin Vignali
Paul B Mahol
Thilo Borgmann
Clément Bœsch
James Almer
Petru Rares Sincraian
Ico Doornekamp
Rostislav Pehlivanov
Ganesh Ajjanagadde
Rodger Combs
Thomas Volkert
Lukasz Marek
Neil Birkbeck
Marton Balint
Clément Bœsch
