Declare IMF format in demuxers #4
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palemieux
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Sep 7, 2021
"frag_start" is redundant, and every occurance can be replaced with cluster[0].dts - start_dts The proof of no behaviour changes: (All line number below is based on commit bff7d66) "frag_start" is read at 4 place (with all possible call stacks): mov_write_packet ... mov_flush_fragment mov_write_moof_tag mov_write_moof_tag_internal mov_write_traf_tag mov_write_tfxd_tag (#1) mov_write_tfdt_tag (#2) mov_add_tfra_entries (#3) mov_write_sidx_tags mov_write_sidx_tag (#4) mov_write_trailer mov_auto_flush_fragment mov_flush_fragment ... (#1 #2 #3 #4) mov_write_sidx_tags mov_write_sidx_tag (#4) shift_data compute_sidx_size get_sidx_size mov_write_sidx_tags mov_write_sidx_tag (#4) All read happens in "mov_write_trailer" and "mov_write_moof_tag". So we need to prove no behaviour change in these two functions. Condition 1: for every track that have "trk->entry == 0", trk->frag_start == trk->track_duration. Condition 2: for every track that have "trk->entry > 0", trk->frag_start == trk->cluster[0].dts - trk->start_dts. Definition 1: "Before flush" means just before the invocation of "mov_flush_fragment", except for the auto-flush case in "mov_write_single_packet", which means before L5934. Lemma 1: If Condition 1 & 2 is true before flush, Condition 1 & 2 is still true after "mov_flush_fragment" returns. Proof: No update to the tracks that have "trk->entry == 0" before flushing, so we only consider tracks that have "trk->entry > 0": Case 1: !moov_written and moov will be written in this iteration trk->entry = 0 L5366 trk->frag_start == trk->cluster[0].dts - trk->start_dts Lemma condition trk->frag_start += trk->start_dts + trk->track_duration - trk->cluster[0].dts; L5363 So trk->entry == 0 && trk->frag_start == trk->track_duration Case 2: !moov_written and moov will NOT be written in this iteration nothing changed Case 3: moov_written trk->entry = 0 L5445 trk->frag_start == trk->cluster[0].dts - trk->start_dts Lemma condition trk->frag_start += trk->start_dts + trk->track_duration - trk->cluster[0].dts; L5444 So trk->entry == 0 && trk->frag_start == trk->track_duration Note that trk->track_duration may be updated for the tracks that have "trk->entry > 0" (mov_write_moov_tag will update track_duration of "tmcd" track, but it must have 1 entry). But in all case, trk->frag_start is also updated to consider the new value. Lemma 2: If Condition 1 & 2 is true before "ff_mov_write_packet" invocation, Condition 1 & 2 is still true after it returns. Proof: Only the track corresponding to the pkt is updated, and no update to relevant variables if trk->entry > 0 before invocation. So we only need to prove "trk->frag_start == trk->cluster[0].dts - trk->start_dts" after trk->entry increase from 0 to 1. Case 1: trk->start_dts == AV_NOPTS_VALUE Case 1.1: trk->frag_discont && use_editlist trk->cluster[0].dts = pkt->dts at L5741 trk->frag_start = pkt->pts at L5785 trk->start_dts = pkt->dts - pkt->pts at L5786 So trk->frag_start == trk->cluster[0].dts - trk->start_dts Case 1.2: trk->frag_discont && !use_editlist trk->cluster[0].dts = pkt->dts at L5741 trk->frag_start = pkt->dts at L5790 trk->start_dts = 0 at L5791 So trk->frag_start == trk->cluster[0].dts - trk->start_dts Case 1.3: !trk->frag_discont trk->cluster[0].dts = pkt->dts at L5741 trk->frag_start = 0 init trk->start_dts = pkt->dts at L5779 So trk->frag_start == trk->cluster[0].dts - trk->start_dts Case 2: trk->start_dts != AV_NOPTS_VALUE Case 2.1: trk->frag_discont trk->cluster[0].dts = pkt->dts at L5741 trk->frag_start = pkt->dts - trk->start_dts at L5763 So trk->frag_start == trk->cluster[0].dts - trk->start_dts Case 2.2: !trk->frag_discont trk->cluster[0].dts = trk->start_dts + trk->track_duration at L5749 trk->track_duration == trk->frag_start Lemma condition So trk->frag_start == trk->cluster[0].dts - trk->start_dts Lemma 3: Condition 1 & 2 is true in all case before and after "ff_mov_write_packet" invocation, before flush and after "mov_flush_fragment" returns. Proof: All updates to relevant variable happen either in "ff_mov_write_packet", or during flush. And Condition 1 & 2 is true initially. So with lemma 1 & 2, we can prove this use induction. Noticed that all read of "frag_start" only happen in "trk->entry > 0" branch. Now we need to prove Condition 2 is true before each read. Because no update to variables relevant to Condition 2 between "before flush" and "mov_write_moof_tag" invocation, we can conclude Condition 2 is true before every invocation of "mov_write_moof_tag". No behaviour change in "mov_write_moof_tag" is proved. In "mov_write_trailer", No update to relevant variables after the last flush and before the invocation of "mov_write_sidx_tag". So no behaviour change to "mov_write_trailer" is proved. Q.E.D. Signed-off-by: Hu Weiwen <[email protected]> Signed-off-by: Martin Storsjö <[email protected]>
palemieux
pushed a commit
that referenced
this issue
Dec 17, 2021
…ion parameter
If memory allocation fails, ERROR(ENOMEM) '-12' will be returned.
When resample() is done first, the negative size param would cause buffer-overflow and SEGV in swri_rematrix().
When swri_rematrix() is run first, resample() would not cause an error but Err num as a wrong parameter passing.
Err num should be returned immediately. And remove an unneeded term from an assert.
coredump info:
#0 0x499517 in posix_memalign (/home/r1/ffmpeg/ffmpeg_4.4.1+0x499517)
#1 0x6c1f0b4 in av_malloc /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavutil/mem.c:86:9
#2 0x6c208fe in av_mallocz /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavutil/mem.c:239:17
#3 0x6c207ad in av_mallocz_array /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavutil/mem.c:195:12
#4 0x654b2e5 in swri_realloc_audio /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libswresample/swresample.c:418:14
#5 0x654f9a1 in swr_convert_internal /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libswresample/swresample.c:601:17
#6 0x654d2c0 in swr_convert /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libswresample/swresample.c:766:19
#7 0x186cf56 in flush_frame /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/af_aresample.c:251:13
#8 0x186a454 in request_frame /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/af_aresample.c:288:20
#9 0x787d9c in ff_request_frame_to_filter /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfilter.c:459:15
#10 0x7877f1 in forward_status_change /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfilter.c:1257:19
#11 0x77ed7e in ff_filter_activate_default /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfilter.c:1288:20
#12 0x77e4e1 in ff_filter_activate /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfilter.c:1441:11
#13 0x793b3f in ff_filter_graph_run_once /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfiltergraph.c:1403:12
#14 0x7a7bee in get_frame_internal /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/buffersink.c:131:19
#15 0x7a7287 in av_buffersink_get_frame_flags /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/buffersink.c:142:12
#16 0x792888 in avfilter_graph_request_oldest /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfiltergraph.c:1356:17
#17 0x5d07df in transcode_from_filter /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:4639:11
#18 0x59e557 in transcode_step /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:4729:20
#19 0x593970 in transcode /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:4805:15
#20 0x58f7a4 in main /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:5010:9
#21 0x7f6fd2dee0b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
SUMMARY: AddressSanitizer: negative-size-param (/home/r1/ffmpeg/ffmpeg_4.4.1+0x497e67) in __asan_memcpy
Reported-by: TOTE Robot <[email protected]>
Signed-off-by: Michael Niedermayer <[email protected]>
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