[FFmpeg-devel] [PATCH 1/2] lavc/bsf: add general documentation

[FFmpeg-devel] [PATCH 1/2] lavc/bsf: add general documentation

[Anton Khirnov]

Also, place the BSF api docs in their own doxygen group.
---
 libavcodec/bsf.h | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/libavcodec/bsf.h b/libavcodec/bsf.h
index 8c5355d186..ba8b48f222 100644
--- a/libavcodec/bsf.h
+++ b/libavcodec/bsf.h
@@ -30,7 +30,28 @@
 #include "packet.h"
 
 /**
- * @addtogroup lavc_core
+ * @defgroup lavc_bsf Bitstream filters
+ * @ingroup libavc
+ *
+ * Bitstream filters transform encoded media data without decoding it. This
+ * allows e.g. manipulating various header values. Bitstream filters operate on
+ * @ref AVPacket "AVPackets".
+ *
+ * The bitstream filtering API is centered around two structures:
+ * AVBitStreamFilter and AVBSFContext. The former represents a bitstream filter
+ * in abstract, the latter a specific filtering process. Obtain an
+ * AVBitStreamFilter using av_bsf_get_by_name() or av_bsf_iterate(), then pass
+ * it to av_bsf_alloc() to create an AVBSFContext. Fill in the user-settable
+ * AVBSFContext fields, as described in its documentation, then call
+ * av_bsf_init() to prepare the filter context for use.
+ *
+ * Submit packets for filtering using av_bsf_send_packet(), obtain filtered
+ * results with av_bsf_receive_packet(). When no more input packets will be
+ * sent, submit a NULL AVPacket to signal the end of the stream to the filter.
+ * av_bsf_receive_packet() will then return trailing packets, if any are
+ * produced by the filter.
+ *
+ * Finally, free the filter context with av_bsf_free().
  * @{
  */
 
-- 
2.34.1

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[FFmpeg-devel] [PATCH 2/2] lavc/bsf: improve doxy

[Anton Khirnov]

---
 libavcodec/bsf.h | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/libavcodec/bsf.h b/libavcodec/bsf.h
index ba8b48f222..611beab885 100644
--- a/libavcodec/bsf.h
+++ b/libavcodec/bsf.h
@@ -167,9 +167,9 @@ const AVBitStreamFilter *av_bsf_iterate(void **opaque);
  * av_bsf_init() before sending any data to the filter.
  *
  * @param filter the filter for which to allocate an instance.
- * @param ctx a pointer into which the pointer to the newly-allocated context
- *            will be written. It must be freed with av_bsf_free() after the
- *            filtering is done.
+ * @param[out] ctx a pointer into which the pointer to the newly-allocated context
+ *                 will be written. It must be freed with av_bsf_free() after the
+ *                 filtering is done.
  *
  * @return 0 on success, a negative AVERROR code on failure
  */
@@ -195,9 +195,11 @@ int av_bsf_init(AVBSFContext *ctx);
  * sending more empty packets does nothing) and will cause the filter to output
  * any packets it may have buffered internally.
  *
- * @return 0 on success. AVERROR(EAGAIN) if packets need to be retrieved from the
- * filter (using av_bsf_receive_packet()) before new input can be consumed. Another
- * negative AVERROR value if an error occurs.
+ * @return
+ *  - 0 on success.
+ *  - AVERROR(EAGAIN) if packets need to be retrieved from the filter (using
+ *    av_bsf_receive_packet()) before new input can be consumed.
+ *  - Another negative AVERROR value if an error occurs.
  */
 int av_bsf_send_packet(AVBSFContext *ctx, AVPacket *pkt);
 
@@ -214,10 +216,12 @@ int av_bsf_send_packet(AVBSFContext *ctx, AVPacket *pkt);
  *                 overwritten by the returned data. On failure, pkt is not
  *                 touched.
  *
- * @return 0 on success. AVERROR(EAGAIN) if more packets need to be sent to the
- * filter (using av_bsf_send_packet()) to get more output. AVERROR_EOF if there
- * will be no further output from the filter. Another negative AVERROR value if
- * an error occurs.
+ * @return
+ *  - 0 on success.
+ *  - AVERROR(EAGAIN) if more packets need to be sent to the filter (using
+ *    av_bsf_send_packet()) to get more output.
+ *  - AVERROR_EOF if there will be no further output from the filter.
+ *  - Another negative AVERROR value if an error occurs.
  *
  * @note one input packet may result in several output packets, so after sending
  * a packet with av_bsf_send_packet(), this function needs to be called
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH 1/2] lavc/bsf: add general documentation

[James Almer]

On 2/22/2022 3:27 AM, Anton Khirnov wrote:
> Also, place the BSF api docs in their own doxygen group.
> ---
>   libavcodec/bsf.h | 23 ++++++++++++++++++++++-
>   1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/bsf.h b/libavcodec/bsf.h
> index 8c5355d186..ba8b48f222 100644
> --- a/libavcodec/bsf.h
> +++ b/libavcodec/bsf.h
> @@ -30,7 +30,28 @@
>   #include "packet.h"
>   
>   /**
> - * @addtogroup lavc_core
> + * @defgroup lavc_bsf Bitstream filters
> + * @ingroup libavc
> + *
> + * Bitstream filters transform encoded media data without decoding it. This
> + * allows e.g. manipulating various header values. Bitstream filters operate on
> + * @ref AVPacket "AVPackets".
> + *
> + * The bitstream filtering API is centered around two structures:
> + * AVBitStreamFilter and AVBSFContext. The former represents a bitstream filter

Could use @ref here and below, too.

> + * in abstract, the latter a specific filtering process. Obtain an
> + * AVBitStreamFilter using av_bsf_get_by_name() or av_bsf_iterate(), then pass
> + * it to av_bsf_alloc() to create an AVBSFContext. Fill in the user-settable
> + * AVBSFContext fields, as described in its documentation, then call
> + * av_bsf_init() to prepare the filter context for use.
> + *
> + * Submit packets for filtering using av_bsf_send_packet(), obtain filtered
> + * results with av_bsf_receive_packet(). When no more input packets will be
> + * sent, submit a NULL AVPacket to signal the end of the stream to the filter.

The doxy for av_bsf_send_packet() states the packet must be "empty", 
meaning either "NULL, or pkt->data is NULL and pkt->side_data_elems 
zero", so probably mention the same here so it's consistent.

> + * av_bsf_receive_packet() will then return trailing packets, if any are
> + * produced by the filter.
> + *
> + * Finally, free the filter context with av_bsf_free().
>    * @{
>    */

LGTM otherwise.
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Re: [FFmpeg-devel] [PATCH 1/2] lavc/bsf: add general documentation

[Anton Khirnov]

Quoting James Almer (2022-02-22 18:09:59)
> 
> 
> On 2/22/2022 3:27 AM, Anton Khirnov wrote:
> > Also, place the BSF api docs in their own doxygen group.
> > ---
> >   libavcodec/bsf.h | 23 ++++++++++++++++++++++-
> >   1 file changed, 22 insertions(+), 1 deletion(-)
> > 
> > diff --git a/libavcodec/bsf.h b/libavcodec/bsf.h
> > index 8c5355d186..ba8b48f222 100644
> > --- a/libavcodec/bsf.h
> > +++ b/libavcodec/bsf.h
> > @@ -30,7 +30,28 @@
> >   #include "packet.h"
> >   
> >   /**
> > - * @addtogroup lavc_core
> > + * @defgroup lavc_bsf Bitstream filters
> > + * @ingroup libavc
> > + *
> > + * Bitstream filters transform encoded media data without decoding it. This
> > + * allows e.g. manipulating various header values. Bitstream filters operate on
> > + * @ref AVPacket "AVPackets".
> > + *
> > + * The bitstream filtering API is centered around two structures:
> > + * AVBitStreamFilter and AVBSFContext. The former represents a bitstream filter
> 
> Could use @ref here and below, too.

That happens automatically when you write a struct name.

> 
> > + * in abstract, the latter a specific filtering process. Obtain an
> > + * AVBitStreamFilter using av_bsf_get_by_name() or av_bsf_iterate(), then pass
> > + * it to av_bsf_alloc() to create an AVBSFContext. Fill in the user-settable
> > + * AVBSFContext fields, as described in its documentation, then call
> > + * av_bsf_init() to prepare the filter context for use.
> > + *
> > + * Submit packets for filtering using av_bsf_send_packet(), obtain filtered
> > + * results with av_bsf_receive_packet(). When no more input packets will be
> > + * sent, submit a NULL AVPacket to signal the end of the stream to the filter.
> 
> The doxy for av_bsf_send_packet() states the packet must be "empty", 
> meaning either "NULL, or pkt->data is NULL and pkt->side_data_elems 
> zero", so probably mention the same here so it's consistent.

The idea here is to provide a quick overview of the API rather than be
exhaustive. In retrospect I regard allowing both NULL and "empty packet"
(for some quite nontrivial definition of empty, given side-data-only
packets) as a mistake, allowing only NULL would be cleaner and less
confusing.

-- 
Anton Khirnov
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Re: [FFmpeg-devel] [PATCH 1/2] lavc/bsf: add general documentation

[James Almer]

On 3/16/2022 8:36 AM, Anton Khirnov wrote:
> Quoting James Almer (2022-02-22 18:09:59)
>>
>>
>> On 2/22/2022 3:27 AM, Anton Khirnov wrote:
>>> Also, place the BSF api docs in their own doxygen group.
>>> ---
>>>    libavcodec/bsf.h | 23 ++++++++++++++++++++++-
>>>    1 file changed, 22 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/libavcodec/bsf.h b/libavcodec/bsf.h
>>> index 8c5355d186..ba8b48f222 100644
>>> --- a/libavcodec/bsf.h
>>> +++ b/libavcodec/bsf.h
>>> @@ -30,7 +30,28 @@
>>>    #include "packet.h"
>>>    
>>>    /**
>>> - * @addtogroup lavc_core
>>> + * @defgroup lavc_bsf Bitstream filters
>>> + * @ingroup libavc
>>> + *
>>> + * Bitstream filters transform encoded media data without decoding it. This
>>> + * allows e.g. manipulating various header values. Bitstream filters operate on
>>> + * @ref AVPacket "AVPackets".
>>> + *
>>> + * The bitstream filtering API is centered around two structures:
>>> + * AVBitStreamFilter and AVBSFContext. The former represents a bitstream filter
>>
>> Could use @ref here and below, too.
> 
> That happens automatically when you write a struct name.
> 
>>
>>> + * in abstract, the latter a specific filtering process. Obtain an
>>> + * AVBitStreamFilter using av_bsf_get_by_name() or av_bsf_iterate(), then pass
>>> + * it to av_bsf_alloc() to create an AVBSFContext. Fill in the user-settable
>>> + * AVBSFContext fields, as described in its documentation, then call
>>> + * av_bsf_init() to prepare the filter context for use.
>>> + *
>>> + * Submit packets for filtering using av_bsf_send_packet(), obtain filtered
>>> + * results with av_bsf_receive_packet(). When no more input packets will be
>>> + * sent, submit a NULL AVPacket to signal the end of the stream to the filter.
>>
>> The doxy for av_bsf_send_packet() states the packet must be "empty",
>> meaning either "NULL, or pkt->data is NULL and pkt->side_data_elems
>> zero", so probably mention the same here so it's consistent.
> 
> The idea here is to provide a quick overview of the API rather than be
> exhaustive. In retrospect I regard allowing both NULL and "empty packet"
> (for some quite nontrivial definition of empty, given side-data-only
> packets) as a mistake, allowing only NULL would be cleaner and less
> confusing.

Ok, LGTM then.
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