Hi,

On 04/12/2012 12:20 PM, Jean-Francois Moine wrote:
> In PJPG blocks, a marker gives the quantization tables to use for image
> decoding. This patch dynamically updates the luminance table when the
> marker changes.
>
> Note that the values of this table have been guessed from a small
> number of images and that they may not work fine in some situations,
> but, in most cases, the images are better.

Thanks for your work on this! I've just spend almost 4 days wrestling
which the Pixart JPEG decompression code to try to better understand
these cams, and I have learned quite a bit and eventually came up
with a different approach.

But your effort is appreciated! After spending so much time on this
myself, I can imagine that it took you quite some time to come up
with your solution.

Attach is a 4 patch patchset which I plan to push to v4l-utils
tomorrow (after running some more tests in daylight). I'll also try
to do some kernel patches tomorrow to match...

Thanks & Regards,

Hans


>
> Signed-off-by: Jean-François Moine<moinejf@free.fr>
>
> diff --git a/lib/libv4lconvert/tinyjpeg-internal.h b/lib/libv4lconvert/tinyjpeg-internal.h
> index 702a2a2..4041251 100644
> --- a/lib/libv4lconvert/tinyjpeg-internal.h
> +++ b/lib/libv4lconvert/tinyjpeg-internal.h
> @@ -103,6 +103,7 @@ struct jdec_private {
>   #if SANITY_CHECK
>   	unsigned int current_cid;			/* For planar JPEG */
>   #endif
> +	unsigned char marker;			/* for PJPG (Pixart JPEG) */
>
>   	/* Temp space used after the IDCT to store each components */
>   	uint8_t Y[64 * 4], Cr[64], Cb[64];
> diff --git a/lib/libv4lconvert/tinyjpeg.c b/lib/libv4lconvert/tinyjpeg.c
> index 2c2d4af..d986a45 100644
> --- a/lib/libv4lconvert/tinyjpeg.c
> +++ b/lib/libv4lconvert/tinyjpeg.c
> @@ -1376,6 +1376,8 @@ static void decode_MCU_2x1_3planes(struct jdec_private *priv)
>   	IDCT(&priv->component_infos[cCr], priv->Cr, 8);
>   }
>
> +static void build_quantization_table(float *qtable, const unsigned char *ref_table);
> +
>   static void pixart_decode_MCU_2x1_3planes(struct jdec_private *priv)
>   {
>   	unsigned char marker;
> @@ -1384,10 +1386,8 @@ static void pixart_decode_MCU_2x1_3planes(struct jdec_private *priv)
>   	/* I think the marker indicates which quantization table to use, iow
>   	   a Pixart JPEG may have a different quantization table per MCU, most
>   	   MCU's have 0x44 as marker for which our special Pixart quantization
> -	   tables are correct. Unfortunately with a 7302 some blocks also have 0x48,
> -	   and sometimes even other values. As 0x48 is quite common too, we really
> -	   need to find out the correct table for that, as currently the blocks
> -	   with a 0x48 marker look wrong. During normal operation the marker stays
> +	   tables are correct. [jfm: snip]
> +	   During normal operation the marker stays
>   	   within the range below, if it gets out of this range we're most likely
>   	   decoding garbage */
>   	if (marker<  0x20 || marker>  0x7f) {
> @@ -1396,6 +1396,53 @@ static void pixart_decode_MCU_2x1_3planes(struct jdec_private *priv)
>   				(unsigned int)marker);
>   		longjmp(priv->jump_state, -EIO);
>   	}
> +
> +	/* rebuild the Y quantization table when the marker changes */
> +	if (marker != priv->marker) {
> +		unsigned char quant_new[64];
> +		int i, j;
> +		/*
> +		 * table to rebuild the Y quantization table
> +		 * 	index 1 = marker / 4
> +		 *	index 2 = 4 end indexes in the quantization table
> +		 *	values = 0x08, 0x10, 0x20, 0x40, 0x63
> +		 * jfm: The values have been guessed from 4 images, so,
> +		 *	better values may be found...
> +		 */
> +		static const unsigned char q_tb[12][4] = {
> +			{ 64, 64, 64, 64 },	/* 68 */
> +			{  8, 32, 64, 64 },
> +			{  1, 16, 50, 64 },
> +			{  1, 16, 30, 60 },	/* 80 */
> +			{  1,  8, 16, 32 },
> +			{  1,  4, 16, 31 },
> +			{  1,  3, 16, 30 },
> +			{  1,  2, 16, 21 },
> +			{  1,  1, 16, 18 },	/* 100 */
> +			{  1,  1, 16, 17 },
> +			{  1,  1, 16, 16 },
> +			{  1,  1, 15, 15 },
> +		};
> +
> +		priv->marker = marker;
> +		j = marker - 68;
> +		if (j<  0)
> +			j = 0;
> +		j>>= 2;
> +		if (j>  sizeof q_tb / sizeof q_tb[0])
> +			j = sizeof q_tb / sizeof q_tb[0] - 1;
> +		for (i = 0; i<  q_tb[j][0]; i++)
> +			quant_new[i] = 0x08;
> +		for (; i<  q_tb[j][1]; i++)
> +			quant_new[i] = 0x10;
> +		for (; i<  q_tb[j][2]; i++)
> +			quant_new[i] = 0x20;
> +		for (; i<  q_tb[j][3]; i++)
> +			quant_new[i] = 0x40;
> +		for (; i<  64; i++)
> +			quant_new[i] = 0x63;
> +		build_quantization_table(priv->Q_tables[0], quant_new);
> +	}
>   	skip_nbits(priv->reservoir, priv->nbits_in_reservoir, priv->stream, 8);
>
>   	// Y
> @@ -1948,6 +1995,7 @@ static int parse_JFIF(struct jdec_private *priv, const unsigned char *stream)
>   		if (!priv->default_huffman_table_initialized) {
>   			build_quantization_table(priv->Q_tables[0], pixart_quantization[0]);
>   			build_quantization_table(priv->Q_tables[1], pixart_quantization[1]);
> +			priv->marker = 68;	/* common starting marker */
>   		}
>   	}
>
>