[FFmpeg-devel] [PATCH] libavformat/mxfenc: Allow more bitrates for NTSC IMX50

[Mark Himsley]

Sorry to drag up this old thread:

On Mon, 19 Aug 2019 at 17:55, Thomas Mundt <tmundt75 at gmail.com> wrote:
...
> I can give you the parameters that I use for IMX50. Not sure if these are
> the best. Got the intra matrix values from an original imx file.
>
> NTSC: -c:v mpeg2video -pix_fmt yuv422p -aspect 16:9 -top 1 -flags
> +ildct+ilme+low_delay -color_range tv -color_trc smpte170m -color_primaries
> smpte170m -colorspace smpte170m -chroma_sample_location topleft
> -signal_standard bt601 -dc 10 -intra_vlc 1 -non_linear_quant 1 -ps 1 -g 1
> -qscale:v 1 -qmin 1 -qmax 12 -b:v 49999841 -minrate 49999841 -maxrate
> 49999841 -bufsize 1668329 -rc_init_occupancy 1668329 -rc_min_vbv_use 1
> -rc_max_vbv_use 1 -profile:v 0 -level:v 5 -intra_matrix
> 8,16,16,17,19,22,23,31,16,16,17,19,20,23,29,29,19,17,19,22,19,25,28,35,17,19,19,20,25,28,25,33,17,19,22,25,26,25,31,31,17,19,17,20,26,28,35,36,19,19,19,20,22,29,32,35,16,17,19,22,25,31,28,45
>
> PAL: -c:v mpeg2video -pix_fmt yuv422p -aspect 16:9 -top 1 -flags
> +ildct+ilme+low_delay -color_range tv -color_trc smpte170m -color_primaries
> bt470bg -colorspace bt470bg -chroma_sample_location topleft
> -signal_standard bt601 -dc 10 -intra_vlc 1 -non_linear_quant 1 -ps 1 -g 1
> -qscale:v 1 -qmin 1 -qmax 12 -b:v 50000000 -minrate 50000000 -maxrate
> 50000000 -bufsize 2000000 -rc_init_occupancy 2000000 -rc_min_vbv_use 1
> -rc_max_vbv_use 1 -profile:v 0 -level:v 5 -intra_matrix
> 8,16,16,17,19,22,23,31,16,16,17,19,20,23,29,29,19,17,19,22,19,25,28,35,17,19,19,20,25,28,25,33,17,19,22,25,26,25,31,31,17,19,17,20,26,28,35,36,19,19,19,20,22,29,32,35,16,17,19,22,25,31,28,45
>
> Regards,
> Thomas

As it stands, FFmpeg from `master` cannot create 30000/1001 FPS IMX50,
and it has to be patched to allow 49999841 to be the valid bitrate,
not 499998410 which is in the source code.
Is there any movement on this issue?
Why is 49999840 in the source code as a variant on 50000000 when it
just does not work?
Is it not better to put 49999841 into the source code?

-- 
Mark Himsley