Re: [FFmpeg-devel] [PATCH v4] lavf/h264: add support for h264 video from Arecont camera, fixes ticket #5154
On 11-05-2019 04:27, Reimar Döffinger wrote: > On Thu, May 09, 2019 at 11:45:59PM +0530, Shivam Goyal wrote: > >> @@ -117,4 +120,128 @@ static int h264_probe(const AVProbeData *p) >> return 0; >> } >> >> +static const uint8_t arecont_sign[] = {0x2D, 0x2D, 0x66, 0x62, 0x64, 0x72, >> 0x0D, 0x0A}; > > I admit I was more thinking of either > static const uint8_t arecont_sign[] = "--fbdr\r\n"; > which ends up 1 byte too long, or > static const uint8_t arecont_sign[8] = "--fbdr\r\n"; > > Though there is also the option to go for > static const uint64_t arecont_sign = AV_RL64("--fbdr\r\n"); > or similar. Okay, I will change it. >> +static int arecont_find_sign(unsigned char *data, int size) > > You should be consistent with the types even if they are essentially > the same. > i.e. uint8_t instead of unsigned char * > Also const, since this function does/should not modify "data". Will change it too, >> +int sign_size = sizeof(arecont_sign) / sizeof(arecont_sign[0]); > > First, this is the expression of number of elements, so the > division part is semantically wrong. > Also it's pointless because it will be 1 always. Will use strlen() as i am changing the above. >> +j = memchr(data, arecont_sign[0], size); >> +while (j != NULL && size - sign_size >= (j - data)) { >> +if (!memcmp(arecont_sign, j, sign_size)) >> +return (j - data); >> +if (size - sign_size == (j - data)) >> +return -1; >> +j = memchr(data + (j - data) + 1, arecont_sign[0], size - (j - >> data)); >> +} > > I know I brought this memchr up, but did you do any benchmarks? > Unless you have actual evidence of a speed problem AND can > show that your solution actually makes it faster, I'd > suggest to go with the simplest possible solution. Yeah, I checked the both approaches and perform test to compare time. and found the previous one is good for shorter strings (length < 300). and the newer version is good for strings larger than this. The newer version is 4 microseconds faster in our case(length ~ 1100). As the diff is small, so i think the simpler version is better. >> +data = av_malloc(size); >> +ret = avio_read_partial(s->pb, data, size); >> +if (ret < 0) { >> +av_free(data); >> +av_packet_unref(pkt); >> +return ret; >> +} >> +if (pos <= ARECONT_H264_MIME_SIZE) { >> +avio_seek(s->pb, 0, SEEK_SET); >> +start = pos; >> +} else { >> +avio_seek(s->pb, pos - ARECONT_H264_MIME_SIZE, SEEK_SET); >> +start = ARECONT_H264_MIME_SIZE; >> +} >> +ret = avio_read_partial(s->pb, data, size); >> +if (ret < 0 || start >= ret) { >> +av_free(data); >> +av_packet_unref(pkt); >> +return ret; >> +} > > Unfortunately I still have no idea what that code is meant to do. > First there is no point in allocating "data" when you have > pkt->data already (yes, it would mean using memmove instead > of memcpy later on, but that seems to be about it). > Then the code reads TWICE into the same buffer for some reason, > the first read seems completely pointless? > Also the only point of the _partial variant of the read function > is reducing latency, however the avio_seek is likely to be > quite a bad hit for latency that this really seems like > premature optimization. > Also the avio_seek means this demuxer might not work at all > if the stream is not seekable (might since I don't know > if we maybe do enough buffering nowadays - but if the code > relies on that there should be a check). What i did in the above code is that as the packet can contain partial http header at the start or end of the pkt, which needs to be removed, i seeked backward 100 bytes( or at the start of the file if necessory) and the i did the same to remove the partial http header at the end, i seeked forward 100 bytes extra. start end stream..^.^ |_| |_| | | http headerhttp header I first filled the "data" and then searched for the http header, copied the bytes before position of http header from "data" to pkt->data. And then skipped the http header and again searched for another http header in "data" and did the same thing. Also, the code is reading twice because the first is just if any errors come( like file ended). because after that the avio_seek() seek stream backwards and if it would do, then error can't be detected. Yeah, i realized that the avio_seek() is not a good idea. One another approach i thought is that to store 100 bytes (or 70) of the current iteration for the next iteration. In this way we don't have to use avio_seek.also there would not be any need of reading twice. Please suggest if it is right. (Sorry, if i am asking too much doubts). >> +
Re: [FFmpeg-devel] [PATCH v4] lavf/h264: add support for h264 video from Arecont camera, fixes ticket #5154
On Thu, May 09, 2019 at 11:45:59PM +0530, Shivam Goyal wrote: > @@ -117,4 +120,128 @@ static int h264_probe(const AVProbeData *p) > return 0; > } > > +static const uint8_t arecont_sign[] = {0x2D, 0x2D, 0x66, 0x62, 0x64, 0x72, > 0x0D, 0x0A}; I admit I was more thinking of either static const uint8_t arecont_sign[] = "--fbdr\r\n"; which ends up 1 byte too long, or static const uint8_t arecont_sign[8] = "--fbdr\r\n"; Though there is also the option to go for static const uint64_t arecont_sign = AV_RL64("--fbdr\r\n"); or similar. > +static int arecont_find_sign(unsigned char *data, int size) You should be consistent with the types even if they are essentially the same. i.e. uint8_t instead of unsigned char * Also const, since this function does/should not modify "data". > +int sign_size = sizeof(arecont_sign) / sizeof(arecont_sign[0]); First, this is the expression of number of elements, so the division part is semantically wrong. Also it's pointless because it will be 1 always. > +j = memchr(data, arecont_sign[0], size); > +while (j != NULL && size - sign_size >= (j - data)) { > +if (!memcmp(arecont_sign, j, sign_size)) > +return (j - data); > +if (size - sign_size == (j - data)) > +return -1; > +j = memchr(data + (j - data) + 1, arecont_sign[0], size - (j - > data)); > +} I know I brought this memchr up, but did you do any benchmarks? Unless you have actual evidence of a speed problem AND can show that your solution actually makes it faster, I'd suggest to go with the simplest possible solution. > +data = av_malloc(size); > +ret = avio_read_partial(s->pb, data, size); > +if (ret < 0) { > +av_free(data); > +av_packet_unref(pkt); > +return ret; > +} > +if (pos <= ARECONT_H264_MIME_SIZE) { > +avio_seek(s->pb, 0, SEEK_SET); > +start = pos; > +} else { > +avio_seek(s->pb, pos - ARECONT_H264_MIME_SIZE, SEEK_SET); > +start = ARECONT_H264_MIME_SIZE; > +} > +ret = avio_read_partial(s->pb, data, size); > +if (ret < 0 || start >= ret) { > +av_free(data); > +av_packet_unref(pkt); > +return ret; > +} Unfortunately I still have no idea what that code is meant to do. First there is no point in allocating "data" when you have pkt->data already (yes, it would mean using memmove instead of memcpy later on, but that seems to be about it). Then the code reads TWICE into the same buffer for some reason, the first read seems completely pointless? Also the only point of the _partial variant of the read function is reducing latency, however the avio_seek is likely to be quite a bad hit for latency that this really seems like premature optimization. Also the avio_seek means this demuxer might not work at all if the stream is not seekable (might since I don't know if we maybe do enough buffering nowadays - but if the code relies on that there should be a check). > +if ((j = arecont_find_sign(data + i, ret - i)) >= 0) { Very personal dislike but: please just don't put assignments into the if. > +k = 0; > +for (w = j + sign_size; w + 1 < ret; w++) { So what exactly happens when you actually end up hitting that loop end condition? It seems to me you then just leave the whole thing in, even though you should have removed it? > +} else > +break; Inverting the condition and putting the 1-line case in the "if" instead of the "else" is much better for readability. In this case it also saves you 1 indentation level. On the general approach: you are scanning a whole, potentially many, many GB large video file for a 8-character string. A false positive has a REALLY high likelihood. I think this needs to be changed into a more clever approach, that actually knows where these strings can appear and removes them in a more targeted way... Best regards, Reimar Döffinger ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
[FFmpeg-devel] [PATCH v4] lavf/h264: add support for h264 video from Arecont camera, fixes ticket #5154
The patch is for ticket #5154. Support for h264 stream from Arecont Camera, The video contains a http header at several places in the stream, which makes it not possible to demux, the structure of the http header is- --fbdr Content-Type: video/H.264I ETag: Channel=1 ( there are two CR+LF characters at the end ) I also detected the stream by detecting this header. For the video to play, i removed the header. The function arecont_find_sign() searches for the signature and returns its position, (-1 when not found ). Also, in the function read_raw_arecont_h264_packet, i used two variables to store data, the 'pkt->data' and 'data'. I first filled the 'data' and find the position of http header ( if it is present) and copied the bytes before the position of the http header, skipped the header, and again did the same thing for rest of the bytes. also as the packet can contain partial header at the beginning and end of the pkt, i took extra size to read from the input stream Please review Thank You Shivam GoyalFrom deb859ff488c500b7e6005e350f04c200f2853a4 Mon Sep 17 00:00:00 2001 From: Shivam Goyal Date: Thu, 9 May 2019 23:18:13 +0530 Subject: [PATCH] lavf/h264: Add support for h264 video from Arecont Camera, Fixes ticket #5154 --- Changelog| 1 + libavformat/Makefile | 1 + libavformat/allformats.c | 1 + libavformat/h264dec.c| 127 +++ libavformat/version.h| 4 +- 5 files changed, 132 insertions(+), 2 deletions(-) diff --git a/Changelog b/Changelog index a3fa0c14a2..0733e360fc 100644 --- a/Changelog +++ b/Changelog @@ -26,6 +26,7 @@ version : - lscr decoder - lagfun filter - asoftclip filter +- Support for raw h264 video from Arecont camera version 4.1: diff --git a/libavformat/Makefile b/libavformat/Makefile index 99be60d184..be0f286870 100644 --- a/libavformat/Makefile +++ b/libavformat/Makefile @@ -99,6 +99,7 @@ OBJS-$(CONFIG_APTX_MUXER)+= rawenc.o OBJS-$(CONFIG_APTX_HD_DEMUXER) += aptxdec.o rawdec.o OBJS-$(CONFIG_APTX_HD_MUXER) += rawenc.o OBJS-$(CONFIG_AQTITLE_DEMUXER) += aqtitledec.o subtitles.o +OBJS-$(CONFIG_ARECONT_H264_DEMUXER) += h264dec.o rawdec.o OBJS-$(CONFIG_ASF_DEMUXER) += asfdec_f.o asf.o asfcrypt.o \ avlanguage.o OBJS-$(CONFIG_ASF_O_DEMUXER) += asfdec_o.o asf.o asfcrypt.o \ diff --git a/libavformat/allformats.c b/libavformat/allformats.c index d316a0529a..fff8083172 100644 --- a/libavformat/allformats.c +++ b/libavformat/allformats.c @@ -60,6 +60,7 @@ extern AVOutputFormat ff_aptx_muxer; extern AVInputFormat ff_aptx_hd_demuxer; extern AVOutputFormat ff_aptx_hd_muxer; extern AVInputFormat ff_aqtitle_demuxer; +extern AVInputFormat ff_arecont_h264_demuxer; extern AVInputFormat ff_asf_demuxer; extern AVOutputFormat ff_asf_muxer; extern AVInputFormat ff_asf_o_demuxer; diff --git a/libavformat/h264dec.c b/libavformat/h264dec.c index 199e87fbfa..99d7f85b40 100644 --- a/libavformat/h264dec.c +++ b/libavformat/h264dec.c @@ -28,6 +28,9 @@ #define MAX_SPS_COUNT 32 #define MAX_PPS_COUNT 256 +#define ARECONT_H264_MIME_SIZE 100 +#define RAW_PACKET_SIZE 1024 + static int h264_probe(const AVProbeData *p) { uint32_t code = -1; @@ -117,4 +120,128 @@ static int h264_probe(const AVProbeData *p) return 0; } +static const uint8_t arecont_sign[] = {0x2D, 0x2D, 0x66, 0x62, 0x64, 0x72, 0x0D, 0x0A}; + +static int arecont_find_sign(unsigned char *data, int size) +{ +unsigned char *j; +int sign_size = sizeof(arecont_sign) / sizeof(arecont_sign[0]); + +j = memchr(data, arecont_sign[0], size); +while (j != NULL && size - sign_size >= (j - data)) { +if (!memcmp(arecont_sign, j, sign_size)) +return (j - data); +if (size - sign_size == (j - data)) +return -1; +j = memchr(data + (j - data) + 1, arecont_sign[0], size - (j - data)); +} +return -1; +} + +static int arecont_h264_probe(const AVProbeData *p) +{ +int ret = h264_probe(p); + +if (!ret) +return 0; +if (arecont_find_sign(p->buf, p->buf_size) >= 0) +return ret + 1; +return 0; +} + +static int read_raw_arecont_h264_packet(AVFormatContext *s, AVPacket *pkt) +{ +int ret, size, start, end, new_size = 0, i = 0, j = 0, k = 0, w = 0; +uint8_t *data; +int64_t pos; +int sign_size = sizeof(arecont_sign) / sizeof(arecont_sign[0]); + +//Extra to find the http header +size = 2 * ARECONT_H264_MIME_SIZE + RAW_PACKET_SIZE; + +if (av_new_packet(pkt, size) < 0) +return AVERROR(ENOMEM); + +pkt->pos = avio_tell(s->pb); +pkt->stream_index = 0; +pos = avio_tell(s->pb); + +data = av_malloc(size); +ret = avio_read_partial(s->pb, data, size); +if (ret < 0) { +av_free(data); +av_packet_unref(pkt); +return ret; +} +if (pos