[FFmpeg-devel] [PATCH 1/3] mjpegenc_common: check for codec ID before using avctx->priv_data

[Michael Niedermayer]

On Mon, Apr 03, 2017 at 09:13:28PM +0100, Rostislav Pehlivanov wrote:
> When coding lossless jpeg the priv context will be pointing to LJpegEncContext
> rather than MpegEncContext, which the function expects.
> 
> Signed-off-by: Rostislav Pehlivanov <atomnuker at gmail.com>
> ---
>  libavcodec/mjpegenc_common.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/libavcodec/mjpegenc_common.c b/libavcodec/mjpegenc_common.c
> index 83a9e95766..6d9c982726 100644
> --- a/libavcodec/mjpegenc_common.c
> +++ b/libavcodec/mjpegenc_common.c
> @@ -91,13 +91,17 @@ static void jpeg_table_header(AVCodecContext *avctx, PutBitContext *p,
>  {
>      int i, j, size;
>      uint8_t *ptr;
> -    MpegEncContext *s = avctx->priv_data;
> +    MpegEncContext *s = NULL;
> +
> +    /* Since avctx->priv_data will point to LJpegEncContext in this case */
> +    if (avctx->codec_id != AV_CODEC_ID_LJPEG)
> +        s = avctx->priv_data;
>  
>      if (avctx->codec_id != AV_CODEC_ID_LJPEG) {
>          int matrix_count = 1 + !!memcmp(luma_intra_matrix,
>                                          chroma_intra_matrix,
>                                          sizeof(luma_intra_matrix[0]) * 64);
> -    if (s->force_duplicated_matrix)
> +    if (s && s->force_duplicated_matrix)
>          matrix_count = 2;
>      /* quant matrixes */
>      put_marker(p, DQT);

> @@ -134,7 +138,7 @@ static void jpeg_table_header(AVCodecContext *avctx, PutBitContext *p,
>  
>      // Only MJPEG can have a variable Huffman variable. All other
>      // formats use the default Huffman table.
> -    if (s->out_format == FMT_MJPEG && s->huffman == HUFFMAN_TABLE_OPTIMAL) {
> +    if (s && s->huffman == HUFFMAN_TABLE_OPTIMAL) {
>          size += put_huffman_table(p, 0, 0, s->mjpeg_ctx->bits_dc_luminance,
>                                    s->mjpeg_ctx->val_dc_luminance);
>          size += put_huffman_table(p, 0, 1, s->mjpeg_ctx->bits_dc_chrominance,

ljpeg uses the same huffman tables as mjpeg,the same
ff_mjpeg_encode_dc()

instead of special casing ljpeg it would be better if the identical
huffman stuff would be shared and the same

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle
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