<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii"> <meta name="Generator" content="Microsoft Word 15 (filtered medium)"> <style></style> </head> <body lang="EN-GB" link="#0563C1" vlink="#954F72"> <div class="WordSection1"> Hello everyone,<o:p></o:p> <o:p> </o:p> I am experimenting with the GstMeta API, am failing badly and would like to appeal to anyone that might be able to assist.<o:p></o:p> <o:p> </o:p> I have created my own GstMeta called GstMyTestMeta for now. This meta has a single guint64 field called testfield.<o:p></o:p> <o:p> </o:p> I am using the following pipeline<o:p></o:p> <o:p> </o:p> videotestsrc ! x264enc ! rtph264pay ! udpsink<o:p></o:p> <o:p> </o:p> I am adding the meta to the buffers as they leave ‘videotestsrc’ using a pad probe, code is below<o:p></o:p> <o:p> </o:p> static GstPadProbeReturn insert_test_meta(GstPad* pad, GstPadProbeInfo* info, gpointer user_data)<o:p></o:p> {<o:p></o:p> GstBuffer* buffer = GST_PAD_PROBE_INFO_BUFFER(info);<o:p></o:p> <o:p> </o:p> GstBuffer* wbuffer = gst_buffer_make_writable(buffer);<o:p></o:p> <o:p> </o:p> /* Making a buffer writable can fail (for example if it<o:p></o:p> * cannot be copied and is used more than once)<o:p></o:p> */<o:p></o:p> if (wbuffer != NULL)<o:p></o:p> {<o:p></o:p> guint64 testfield = 12345;<o:p></o:p> <o:p> </o:p> GstMyTestMeta* meta = gst_buffer_add_my_test_meta(wbuffer, testfield);<o:p></o:p> <o:p> </o:p> G_print("Added meta with timestamp %ld", meta->testfield);<o:p></o:p> }<o:p></o:p> <o:p> </o:p> return GST_PAD_PROBE_OK;<o:p></o:p> }<o:p></o:p> <o:p> </o:p> I would like to access the meta as it leaves the rtph264pay, again using a pad probe, and add it to the RTP Header as a Header Extension, code is below<o:p></o:p> <o:p> </o:p> static GstPadProbeReturn convert_test_meta_to_rtp_header_extension(GstPad* pad, GstPadProbeInfo* info, gpointer user_data)<o:p></o:p> {<o:p></o:p> GstBuffer* buffer;<o:p></o:p> <o:p> </o:p> buffer = GST_PAD_PROBE_INFO_BUFFER(info);<o:p></o:p> <o:p> </o:p> buffer = gst_buffer_make_writable(buffer);<o:p></o:p> <o:p> </o:p> /* Making a buffer writable can fail (for example if it<o:p></o:p> * cannot be copied and is used more than once)<o:p></o:p> */<o:p></o:p> if (buffer == NULL)<o:p></o:p> return GST_PAD_PROBE_OK;<o:p></o:p> <o:p> </o:p> GstRTPBuffer rtp_buffer = GST_RTP_BUFFER_INIT;<o:p></o:p> <o:p> </o:p> if (gst_rtp_buffer_map(buffer, GST_MAP_READWRITE, &rtp_buffer))<o:p></o:p> { <o:p></o:p> GstMyTestMeta *meta = gst_buffer_get_my_test_meta(buffer);<o:p></o:p> <o:p> </o:p> gchar* data = g_strdup_printf("%ld", meta->testfield);<o:p></o:p> <o:p></o:p> gboolean added = gst_rtp_buffer_add_extension_onebyte_header(&rtp_buffer, 1, data, strlen(data));<o:p></o:p> <o:p></o:p> gst_rtp_buffer_unmap(&rtp_buffer);<o:p></o:p> <o:p> </o:p> g_free(data);<o:p></o:p> }<o:p></o:p> <o:p> </o:p> return GST_PAD_PROBE_OK;<o:p></o:p> }<o:p></o:p> <o:p> </o:p> I have stepped through the code and know that the meta is being added to the buffer ok, and confirmed by debug output. However, my program crashes with a memory access violation exception before the second pad probe callback is invoked.<o:p></o:p> <o:p> </o:p> The relevant part of the debug output is show below. There is more output before the first entry but no more after the last room.<o:p></o:p> <o:p> </o:p> 0:00:01.361461200 27732 057F9730 DEBUG GST_META gstmeta.c:88:gst_meta_api_type_register: register API "GstMyTestMetaAPI"<o:p></o:p> 0:00:01.361520300 27732 057F9730 DEBUG GST_META gstmeta.c:198:gst_meta_register: register "GstMyTestMeta" implementing "GstMyTestMetaAPI" of size 8<o:p></o:p> 0:00:01.361558300 27732 057F9730 DEBUG GST_BUFFER gstbuffer.c:2281:gst_buffer_add_meta: alloc metadata 05385E70 (GstMytestMeta) of size 8<o:p></o:p> 0:00:01.362175400 27732 057F9730 DEBUG GST_PADS gstpad.c:3601:probe_hook_marshal:<videotestsrc0:src> probe returned OK<o:p></o:p> 0:00:01.362241300 27732 057F9730 DEBUG GST_SCHEDULING gstpad.c:4324:gst_pad_chain_data_unchecked:<x264enc0:sink> calling chainfunction &gst_video_encoder_chain with buffer buffer: 05827358, pts 0:00:00.000000000, dts 99:99:99.999999999, dur 0:00:00.033333333, size 230400, offset 0, offset_end 1, flags 0x40<o:p></o:p> 0:00:01.362289400 27732 057F9730 LOG videoencoder gstvideoencoder.c:1465:gst_video_encoder_chain:<x264enc0> received buffer of size 230400 with PTS 0:00:00.000000000, DTS 99:99:99.999999999, duration 0:00:00.033333333<o:p></o:p> 0:00:01.362332000 27732 057F9730 LOG videoencoder gstvideoencoder.c:1552:gst_video_encoder_chain:<x264enc0> passing frame pfn 0 to subclass<o:p></o:p> 0:00:01.362372200 27732 057F9730 LOG GST_BUFFER gstbuffer.c:1798:gst_buffer_map_range: buffer 05827358, idx 0, length 1, flags 0001<o:p></o:p> 0:00:01.362407300 27732 057F9730 LOG GST_BUFFER gstbuffer.c:242:_get_merged_memory: buffer 05827358, idx 0, length 1<o:p></o:p> 0:00:01.362442600 27732 057F9730 LOG GST_BUFFER gstbuffer.c:1798:gst_buffer_map_range: buffer 05827358, idx 0, length 1, flags 0001<o:p></o:p> 0:00:01.362480900 27732 057F9730 LOG GST_BUFFER gstbuffer.c:242:_get_merged_memory: buffer 05827358, idx 0, length 1<o:p></o:p> 0:00:01.362515500 27732 057F9730 LOG GST_BUFFER gstbuffer.c:1798:gst_buffer_map_range: buffer 05827358, idx 0, length 1, flags 0001<o:p></o:p> 0:00:01.362549600 27732 057F9730 LOG GST_BUFFER gstbuffer.c:242:_get_merged_memory: buffer 05827358, idx 0, length 1<o:p></o:p> 0:00:01.362587600 27732 057F9730 DEBUG GST_META gstmeta.c:88:gst_meta_api_type_register: register API "GstVideoCaptionMetaAPI"<o:p></o:p> 0:00:01.362628600 27732 057F9730 LOG GST_DEBUG gstinfo.c:1604:gst_debug_apply_entry: category video-anc matches pattern 01049A70 - gets set to level 6<o:p></o:p> 0:00:01.362664600 27732 057F9730 INFO video-anc video-anc.c:859:gst_video_caption_meta_api_get_type: registering<o:p></o:p> <o:p> </o:p> <o:p> </o:p> I have searched for examples on how to use the GstMeta API but without any success. I believe that it is the intention of this API to support this use case but I am unsure.<o:p></o:p> <o:p> </o:p> I would greatly appreciate any help or assistance that anyone is able to offer.<o:p></o:p> <o:p> </o:p> Kind Regards<o:p></o:p> <o:p> </o:p> Jon Lovewell<o:p></o:p> <o:p> </o:p> <o:p> </o:p> </div> </body> </html>