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.jpg
  http://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.pcap
  http://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>

Everything except ORing the sign is now done in the LUT.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Simplifies code
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>

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

No idea why in commit 01ecb717 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>

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Fixes trac #4828

Part of trac #4828

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>

Found-by: wm4
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

It could theoretically contain invalid data that gets ignored by decoders.

Testset provided by Justin Greer <justin@zencoder.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>

avformat/utils: scan a bit farther for a keyframe in mpeg/mpegts (7 sec instead of 5, we already scan 90sec in some cases by default)

Fixes Ticket5305
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

The count_hq_slice() function is always used with a SliceArgs struct
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

Fixes trac bug #5353

Uninitialized memory for the initial quantization index
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>

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Related to ticket #2324, #2325.

Stream duration still need to be fixed...
Signed-off-by: Marton Balint <cus@passwd.hu>

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Marton Balint <cus@passwd.hu>

Signed-off-by: Marton Balint <cus@passwd.hu>

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.

dv_extract_video_info() is a static function called only from
avpriv_dv_produce_packet(), where c->sys is made sure to be set.

Reviewed-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Needed for noStreams.wtv unless something else forces continued parsing (like looking for more than 1
frame in attachments)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Remove achroma filter, as same output can be done with lowpass filter
and multiple components with overlay display.
Signed-off-by: Paul B Mahol <onemda@gmail.com>

Fixes Ticket5287
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>