Allocate an AVCodecContext and set its fields to default values. The
resulting struct should be freed with avcodec_free_context().
@param codec if non-NULL, allocate private data and initialize defaults
for the given codec. It is illegal to then call avcodec_open2()
with a different codec.
If NULL, then the codec-specific defaults won't be initialized,
which may result in suboptimal default settings (this is
important mainly for encoders, e.g. libx264).
@return An AVCodecContext filled with default values or NULL on failure.
Allocate an AVCodecContext and set its fields to default values. The resulting struct should be freed with avcodec_free_context().
@param codec if non-NULL, allocate private data and initialize defaults for the given codec. It is illegal to then call avcodec_open2() with a different codec. If NULL, then the codec-specific defaults won't be initialized, which may result in suboptimal default settings (this is important mainly for encoders, e.g. libx264).
@return An AVCodecContext filled with default values or NULL on failure.